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This paper explores the propagation loss in waveguides on directly bonded InP/Si substrates, using numerical simulations to understand the effect of voids within the waveguide structure. Using COMSOL Multiphysics, we developed a model to simulate light propagation, focusing on how void characteristics such as diameter and angle influence the propagation loss. Our findings reveal a correlation between void dimensions and the increased threshold current density in separate confinement heterostructure multiple quantum well laser diodes, thereby providing insights into optimizing waveguide design for enhanced laser performance on InP/Si substrates. This research underscores the critical role of substrate bonding quality in minimizing internal losses and improving device efficiency. [ABSTRACT FROM AUTHOR]

The vertical gradient freeze (VGF) process needs to regulate the temperature field more accurately to ensure the successful seed crystal introduction and good crystal growth condition compared to the vertical Bridgman method, such as a suitable solid–liquid interface temperature gradient. This work presents a method for regulation of the temperature field via temperature control of six heaters during VGF growth of InP crystal with numerical simulation, and shows the involution for both the melt convection and the solid–liquid interface temperature gradient. Two of the six heaters were in the heating zone, two in the gradient zone, and the others in the cooling zone. Firstly, three temperature settings for the six heaters were selected through many trial calculations to ensure the success of seed crystal introduction. Secondly, their effects on the temperature field in the crucible and the convection in the melt were investigated. The results show that the axial temperature gradient in the melt increases with an increase in the heating zone temperature or a decrease in the cooling zone temperature, of which the maximum for each simulation experiment almost always appears at the solid–liquid interface and decreases continuously with the crystal growth process. Moreover, the maximum temperature gradient in the melt for all the simulations is well below 10 K/cm due to the shouldering stage 2, which cannot improve significantly even if the heating zone temperature increases and the cooling zone temperature decreases to room temperature. The temperature setting of the heaters has no significant influence on the convection pattern in the melt, which is nearly the same for all three settings. However, the maximum velocity of the convection field increases significantly with the axial temperature gradient increase. The number of convective vortices in the melt decreases from four at the initial seeding stage to one at the end of the equal-diameter growth for every simulation, but the maximum flow velocity decreases very slowly from the shouldering stage. [ABSTRACT FROM AUTHOR]

We have evaluated InGaAs/InP PIN (p-I-n) photodiodes failed by electrostatic discharge (ESD) with forward or reverse biasing, using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive x-ray spectrometry (EDX), Raman spectroscopy, and photoluminescence (PL) imaging. First, localized traces and bumps were observed on the surface of the Au electrode by SEM. Next, by cross-sectional STEM observation, a heavily damaged region including a void was observed in the p+-InP layer and an upper part of the n−-InGaAs layer just below the bump on the Au electrode. Cross-sectional EDX mapping indicated that the damaged region consists of a mixture of InP and InGaAs, i.e., InGaAsP quaternary material. In addition, poor crystal quality of the active PIN region was also revealed by Raman spectroscopy and PL imaging. Furthermore, although similar results were obtained for the ESD-failed samples with application of both forward and reverse bias, the magnitude of the ESD damage is larger in the case of forward bias as compared with the case of reverse bias. On the basis of these results, we propose a possible ESD failure mechanism that is associated with significant Joule heating in the p+-InP layer and the upper part of the n−-InGaAs layer due to the local concentration of a large current. [ABSTRACT FROM AUTHOR]

A self-powered ITO/ZnO/InP heterojunction photodetector has been demonstrated with a 10-nm ZnO interfacial layer deposited by atomic layer deposition as a hole-blocking layer. The presence of a valence band offset between InP and ZnO enhances the photocurrent. The valence band offset between InP and ZnO creates a sufficient barrier for hole movement. Low surface recombination under 520-nm laser irradiation produced maximum photoresponsivity of 44.2 mAW−1 with an illumination power of 1 µW at zero bias. The ZnO-passivated self-powered photodetector shows fast response and improved photo-detecting properties. Furthermore, the highly sensitive photodetectors are demonstrated to record the heart pulse wave by measuring relative changes in blood volume of the finger vessels. [ABSTRACT FROM AUTHOR]

We demonstrated the feasibility of using InP (100) substrates, a different indium source, for the synthesis of In2O3 nanowires by the vapor–liquid–solid (VLS) method using a 20-nm-thick Au layer as a catalyst. By varying the thickness of the Au layer and the growth temperature (T), the nanowires showed different morphologies. The nanowires grew along the (100) direction and had perfect crystallinity and lengths up to several hundreds of micrometers. The configured field-effect transistor revealed an n-type behavior with 115 μA of the drain-source current, IDS, under 1.0 V of gate voltage, VDS, at 1.33 × 10−4 kPa of pressure and temperature of 20°C. This result indicates that it is feasible to use different In sources to synthesize In2O3 nanowires by the VLS method for electronic devices. [ABSTRACT FROM AUTHOR]

A high-responsivity 3D graphene/InGaAs/InAs/InAlAs/Insb/InP HEMT two-dimensional electron gas (2DEG) photodetector is investigated and simulated using DevEdit and ATLAS 3D under SILVACO Tools. The InAs donor layer above the 2DEG contributes to the photocurrent using the InSb channel layer and graphene in the gate for light absorption. An illumination drain current equal to 57.5 mA was obtained with a rejection ratio (illumination current/dark current) equal to 1.02 A/W and 0.5 × 10−6 A/W available photocurrent, with high responsivity equal to 15.3 × 103 A/W at 100 nm wavelength and 100 GHz bandwidth. This property makes the device a suitable candidate for detection in the UV region of the spectrum. It can also be used in a number of medical, military and space applications. [ABSTRACT FROM AUTHOR]

This paper compares the electronic transport proprieties of two materials, InP and InAs0.3P0.7, in order to present the advantageous characteristics of InAs0.3P0.7 and which in turn leads to inventing of a first substrate derived from InP. This comparative study is performed by using Monte Carlo methods at room temperature and includes the acoustic, polar and inter-valley scattering mechanisms, as well as the energy and drift velocity of charge carriers. The obtained results show that InAs0.3P0.7 presents better behavior in terms of charge carrier energy and drift velocity compared to InP, due to its low set energy describing the band energy of InAs0.3P0.7, as well as high atomic density. On the other hand, the registered energy saturation for charges carriers in the case of InAs0.3P0.7 is reached quickly and under lower applied electric fields compared to InP, due to its high rate of scattering, making InAs0.3P0.7 better than InP for use in high-frequency and low-power operation applications. [ABSTRACT FROM AUTHOR]

A rectifying junction was prepared by casting a drop of colloidal graphite on the surface of an InP substrate. The electrophysical properties of graphite/InP junctions were investigated in a wide temperature range. Temperature-dependent I-V characteristics of the graphite/InP junctions are explained by the thermionic emission mechanism. The Schottky barrier height (SBH) and the ideality factor were found to be 0.9 eV and 1.47, respectively. The large value of the SBH and its weak temperature dependence are explained by lateral homogeneity of the junction, which is related to the structure of the graphite layer. The moderate disagreement between the current-voltage and capacitance-voltage measurements is attributed to the formation of interfacial native oxide film on the InP surface. [ABSTRACT FROM AUTHOR]

We report the crystallization and phase-transition behavior of GeSbTe thin films doped with indium phosphorus (InP). Pure GeSbTe thin films and InP-doped GeSbTe thin films were prepared by use of an rf magnetron sputtering method. After thermal annealing, electrical and optical changes in the thin films were observed. Sheet resistance and reflectance measurements revealed that InP doping suppresses crystallization of GeSbTe. X-ray diffraction analysis confirmed that addition of In and P atoms inhibits the phase transition from face-centered cubic to hexagonal closed-packed. Nucleation of the doped GeSbTe thin films was delayed at an annealing temperature of 100°C; after thermal annealing, neither segregation nor formation of a secondary phase occurred. These results indicate that InP doping improves the amorphous stability of GeSbTe thin films. It is believed this enhanced amorphous stability is a result of the formation of multiple, strong crosslinks by the In and P atoms. [ABSTRACT FROM AUTHOR]

Heteroepitaxy of InP on Si by epitaxial lateral overgrowth (ELOG) using a thin seed layer of InP as starting material is investigated, with special attention given to the effect of the surface morphology of the seed and the mask layers on the quality of the ELOG layers. Chemical mechanical polishing (CMP) has been used to improve the morphological and optical quality of InP grown by hydride vapor-phase epitaxy (HVPE) using ELOG. Two approaches have been investigated: polishing the InP seed layer on Si before depositing the SiO2 mask and polishing the SiO2 mask after its deposition on the unprocessed seed layer. For polishing the InP (seed)/Si, a two-step process with an aluminum oxide- and sodium hypochlorite-containing slurry as well as a slurry based on sodium hypochlorite mixed with citric acid was used. For SiO2 mask polishing, a slurry with colloidal silica as an abrasive was employed. In both cases, the SiO2 mask was patterned with double line openings and ELOG carried out in an HVPE reactor. Morphology and crystal quality of the resulting ELOG layers were studied with atomic force microscopy (AFM) and room-temperature panchromatic cathodoluminescence (PC-CL) in situ in a scanning electron microscope (SEM), respectively. The results show that, whereas both polishing approaches result in an ELOG InP layer with good morphology, its surface roughness is lower when the InP (seed)/Si is subjected to CMP prior to deposition of the SiO2 mask, than when only the SiO2 mask is polished. This approach also leads to a decrease in the number of defects generated during coalescence of the ELOG layers. [ABSTRACT FROM AUTHOR]

We investigated the effect of deep-etched mesa sidewall profile and oxide overhang length on the regrowth structural characteristics for buried- heterostructure (BH) quantum cascade lasers (QCLs) grown by metalorganic chemical vapor deposition (MOCVD). The relationship between etched mesa sidewall geometry, oxide overhang length, oxide thickness, and growth uniformity was examined and is extensively discussed. In particular, anomalous growth in the vicinity of the oxide edge resulting from insufficient oxide overhang length was identified and studied. An ideal ratio of mesa height to oxide overhang length between 2.5 and 3.0 is proposed and experimentally justified to yield satisfactory planar regrowths without anomalous growth. Mesas in the [011-] direction with smoothly etched entrant profile yield a higher degree of growth uniformity than mesas in the [011] direction with the re-entrant profile. [ABSTRACT FROM AUTHOR]

To reduce base resistance of an InP/InGaAs heterojunction bipolar transistor grown by gas-source molecular beam epitaxy, the doping characteristics of carbon-doped InGaAs and the dependence of doping concentration on current gain were investigated. Using a thicker graded base was found to increase current gain significantly, resulting in increased doping level in the InGaAs: C-base layer. In particular, an 80-nm-thick graded base produces a base sheet resistance of 285 Ω/sq and maintains a practically useful current gain of 23 and a high cut-off frequency of 139 GHz. [ABSTRACT FROM AUTHOR]

Low-bandgap, lattice-mismatched GaxIn1-xAs (GaInAs) grown using InAsyP1-y, (InAsP) compositional-step grades on InP is a primary choice for light-absorbing, active layers in high-efficiency thermophotovoltaic (TPV) devices. The GaInAs/InAsP double heterostructures (DHs) show exceptional minority carrier lifetimes of up to several microseconds. We have performed a characterization survey of 0.4-0.6-eV GaInAs/InAsP DHs using a variety of techniques, including transmission electron microscopy (TEM). Dislocations are rarely observed to thread into the GaInAs active layers from the InAsP buffer layers that terminate the graded regions. Nearly complete strain relaxation occurs in buried regions of the InAsP grades. The buffer-layer strain prior to deposition of the active layer is virtually independent of the net misfit. Foreknowledge of this buffer-layer strain is essential to correctly lattice match the buffer to the GaInAs active layer. [ABSTRACT FROM AUTHOR]

In this paper, InP metal-oxide-semiconductor (MOS) structures are fabricated by transferring thermally grown SiO2 to InP from oxidized Si wafers using oxygen plasma assisted wafer bonding followed by annealing at either 125°C or at 400°C. Well-defined accumulation and inversion regions in recorded capacitance-voltage (C-V) curves were obtained. The long-term stability was comparable to what has been previously reported. The structures exhibited high breakdown fields, equivalent to thermally grown SiO2-Si MOS structures. The transferring process was also used to fabricate bonded Si MOS structures. [ABSTRACT FROM AUTHOR]

Strained AlxIn1−xAs/Ga0.47In0.53As heterojunction N-p+ diodes and heterojunction bipolar transistors (HBTs) have been grown on InP substrates by solid-source molecular-beam epitaxy, fabricated, and characterized. To determine the effects of the conduction-band discontinuity at the emitter-base heterojunction on turn-on voltage and ideality factor, a strained Al0.7In0.3As layer is inserted in the emitter near the base. Changes in transport across the junction are observed as a function of the strained-layer position and thickness. These results were used to implement strained emitter HBTs. [ABSTRACT FROM AUTHOR]

Zinc incorporation by post-growth metalorganic vapor phase diffusion (MOVPD) is used to achieve high p-doping, which is desirable for the fabrication of photodiodes. Diethylzinc (DEZ) is used as precursor and Zn is diffused into InP and InAs0.6P epitaxial layers grown by low pressure metalorganic vapor phase epitaxy (MOVPE) on different substrate orientations, enabling the investigation of the dislocation density on the Zn incorporation. Diffusion depths are measured using cleave-and-stain techniques, resistivity measurements, electrochemical profiling, and secondary ion mass spectroscopy. High hole concentrations of, respectively, 1.7 1019 and 6 1018 cm−3, are obtained for, respectively, InAs0.60P and InP. The diffusion coefficients are derived and the Zn diffusion is used for the fabrication of lattice-mismatched planar PIN InAsP/InGaAs photodiodes. [ABSTRACT FROM AUTHOR]

We report the characteristics of InP self-assembled quantum dots embedded in In0.5Al0.5P on GaAs substrates grown by metalorganic chemical vapor deposition. The InP quantum dots show increased average dot sizes and decreased dot densities, as the growth temperature increases from 475°C to 600°C with constant growth time. Above the growth temperature of 600°C, however, dramatically smaller and densely distributed self-assembled InP quantum dots are formed. The small InP quantum dots grown at 650°C are dislocation-free “coherent” regions with an average size of ∼20 nm (height) and a density of ∼1.5 × 108 mm−2. These InP quantum dots have a broad range of luminescence corresponding to red or organge in the visible spectrum. [ABSTRACT FROM AUTHOR]

MOCVD growth of InxGa1−xAs from trimethylgallium (TMG), triethylgallium (TEG), trimethylindium (TMI) and arsine was studied over a wide range of growth conditions. It was found that the InxGa1−xAs strain with respect to InP is strongly influenced by the arsine concentration when grown with TEG and TMI. In contrast the InxGa1−xAs strain was independent of arsine concentration when grown with TMG and TMI. It was also observed that the growth rate of InxGa1−xAs is higher for TMG than for TEG with the same TMI and arsine flow. In addition an interaction between TEG and dimethylzinc (DMZ) was also observed. We show that MOCVD growth process involves many complex reactions and cannot be considered as a simple decomposition of each precursor. The interactions between precursors, which takes place in the gas phase or on the growing surface, has to be considered. We have utilized the TEG/arsine interaction for the growth of strain compensated superlattices by modulating the arsine flow into the reactor chamber while keeping the TEG and TMI constant. Structures with up to 100 periods of 100 Å of +1% In0.6Ga0.4As and 200 Å of −0.5% In0.5Ga0.5As were grown with excellent characteristics. [ABSTRACT FROM AUTHOR]

Bromineion-beam-assisted etching produces smooth vertical sidewalls in GaAs, GaP, InP, AlSb, and GaSb as well as in the usual alloys formed from these materials. Care must be taken, however, during etching to match the specific material system with an appropriate substrate etch temperature. For example, vertical walls were obtained using substrate temperatures in the range of 150 to 200°C with InP, 80 to 140°C with GaAs and GaP, and below 30°C with AlSb and GaSb. GaN has also been etched with the technique. Our etching experience and the vapor pressure data for bromine with group III and group V elements lead us to believe that all of the various technologically important III-V binaries, ternaries, and quaternaries can be etched. Etch rates of most of the materials can be varied from several nm/min to 0.16 µm/min through the bromine flow rate, Ar+ ion beam density and energy, and the substrate temperature. Bromine ion-beam-assisted etching also appears to have an advantage over chlorine ion-beam-assisted etching in many situations, in that substrate temperature ranges can be found for which vertical sidewalls are maintained while etching through layered structures composed of various alloys of the materials. Here we present results obtained from etching a number of III-V binaries, alloys, and heterostructures. [ABSTRACT FROM AUTHOR]

The uniformity of deep levels in semi-insulating InP wafers, which have been obtained by multiple-step wafer annealing under phosphorus vapor pressure, was studied using the thermally stimulated current (TSC) and photoluminescence (PL) methods. Only three traps related to Fe, T0 (ionization energy Ei=0.19 eV), T1 (0.25 eV), and T2 (0.33 eV), probably forming complex defects, were observed in the wafer and they exhibited a relatively uniform distribution. PL spectra relating to phosphorus vacancies observed in some regions of the wafer are correlated with a small TSC signal having an ionization energy of 0.43 eV. [ABSTRACT FROM AUTHOR]

Using secondary ion mass spectrometry (SIMS), we have investigated the excess group V content in GaAs and InP films grown by molecular beam epitaxy at low temperature. Using the inherent depth profiling capability of SIMS, we investigated the V/III ratio in films grown at nominally constant temperatures and also in films grown with stepped temperature profiles. Thickness profiles of the V/III ratio show the effects of intentional temperature changes and of an unintentional drift in the actual substrate temperature during growth. The ability to measure as little as 0.1% excess As and about 0.2% excess P indicates excellent measurement resolution. SIMS analysis is also used to identify a narrow growth temperature range over which InP can be grown with appreciable nonstoichiometry yet remain monocrystalline. [ABSTRACT FROM AUTHOR]

Galvanic corrosion effects in metallized III-V laser structures have been studied. Small gaps present in the metallization can leave exposed semiconductor regions, which are susceptible to localized corrosion in the presence of an electrolyte. Electochemical measurements in two different electrolytes, i.e., 1% HF and concentrated H3PO4, were made of test structures comprised of n-type InP, p-type InP, and p-type InGaAs, as well as Au. Polarization measurements were made in all cases relative to a Ag/AgCl reference electrode. Corrosion potentials, measured relative to Au, of 540, 180, and 330 mV were obtained for n-type InP, p-type InP, and p-type InGaAs, respectively, in 1% HF. Values of 415, 47, and 138 mV were obtained for n-type InP, p-type InP, and p-type InGaAs, respectively, in concentrated H3PO4. Galvanic current densities of 2.0 × 10−6A/cm2, 1.0 × 10−7 A/cm2, and 4.0 × 10−6 A/cm2 were obtained for galvanic couples of n-type InP/Au, p-type InP/Au, and p-type InGaAs/Au, respectively, in 1%HF. Values of 1.2 × 10−6 A/cm2, 1.2 × 10−7 A/cm2, and 1.0 × 10−6 A/cm2 were obtained for galvanic couples of n-type InP/Au, p-type InP/Au, and p-type InGaAs/Au, respectively, in concentrated H3PO4. Complementary microstructural studies, using scanning electron microscopy, were done on actual metallized ridge laser structures, consisting of a p-type InP ridge with a p-type InGaAs capping layer and a Ti/Pt/Au metallization. Localized pitting of the InGaAs layer was observed for samples with gaps in the metallization. [ABSTRACT FROM AUTHOR]

Recently, it was found that undoped semi-insulating InP can be reproducibly obtained by wafer annealing at 950°C for 40 h under phosphorus vapor pressure of 1 atm. Resistivity variation across the 50 mm diameter wafer after this annealing process, however, was in the range of 22.5–53.7%. In order to realize the fabrication of undoped semi-insulating (SI) InP with uniform electrical properties, multiple-step wafer annealing (MWA) procedure has been applied for the first time. It was found that two-step wafer annealing at 950°C for 40 h under phosphorus vapor pressure of 1 atm and at 807°C for 40 h under phosphorus vapor pressure ranging from 30 to 50 atm, was effective in improvement of the uniformity of the electrical properties of undoped SI InP. By the present MWA, the resistivity variation of 8–12% and the mobility variation of 2–4% could be obtained for 50 mm diameter wafers. [ABSTRACT FROM AUTHOR]

Ternary phase diagrams have proven valuable for understanding the reactions between a metal contact and a compound semiconductor, as well as for choosing thermally stable electrical contacts in thermodynamic equilibrium with the semiconductor. Since InP is important for both optoelectronic and electronic devices, the metal-In-P systems are of particular interest. In this work, new portions of isothermal sections of the (Rh, Ir, Ru, Os)-In-P diagrams are presented. Then, since no compilation of the published metal-In-P phase diagrams is available, the diagrams are reviewed here. The features of these diagrams are discussed in terms of the thermodynamics of the metal-In-P systems, particularly the considerable thermodynamic stability of many of the transition metal phosphides. Finally, some of the phases in thermodynamic equilibrium with InP, particularly PdIn and Ni2P, are highlighted for their potential for high-temperature contacts to InP. [ABSTRACT FROM AUTHOR]

The thermal stability of tellurium in InP has been examined in samples doped with Te up to an electron concentration of 1.4 × 1020 cm−3. Annealing was conducted using rapid thermal annealing for a period of one minute at temperatures over the range 650–800°C. Secondary ion mass spectroscopy analysis showed virtually no change in the Te profile before and after annealing, even at the highest annealing temperatures. High resolution x-ray diffraction and Hall measurements revealed a general decrease in the lattice strain and carrier concentration for annealing temperatures above 650°C. No evidence of strain relief was found in the form of cross-hatching or through the formation of a dislocation network as examined by scanning electron microscopy or transmission electron microscopy (TEM). These results are most likely due to the formation of Te clusters, though such clusters could not be seen by crosssectional TEM. [ABSTRACT FROM AUTHOR]

Reflectance anisotropy spectroscopy (RAS) has been used to study the metalorganic vapor phase epitaxy growth process for GaxIn1−xAsyP1−y/InP light emitting diodes. The sensitivity of RAS to morphology changes is demonstrated by InP growth on different InP:Fe substrates. RAS reveals not only development of dull surfaces but also detects initial temporary roughness of mirror-like layers. Based on the RAS results the substrate preparation was optimized. RAS spectra measured on n- and p-type InP and p-type GaInAsP during light emitting diodes production are suitable for finger-printing of the growth process. Spectra from InP:Si and InP:Zn layers show characteristic features near 4.3 eV which allow for assessment of doping level at growth temperature (640°C). Correlation of RAS spectra and transients during growth with the quaternary composition was achieved. A change in composition of only Δx=0.01, Δy=0.03 corresponding to a shift of photoluminescence-peak position by 16 nm was detectable in RAS spectra. The results demonstrate the high sensitivity and thus the suitability of RAS for on-line control during growth of device structures. [ABSTRACT FROM AUTHOR]

The effect of the growth temperature on the quality of InP grown by chemical beam epitaxy (CBE) using ethyldimethylindium (EDMIn) and bisphos-phinoethane (BPE) are presented. The growth rate was nearly independent of growth temperature, BPE flow rate, and cracker cell temperature in the range from 700 to 900°C. Smooth and mirror-like surfaces were obtained for all of the samples grown at temperatures above 465°C. All of the InP samples were n-type. As the growth temperature increased, the net carrier concentration decreased and reached a minimum value of 3.2× 1015 cm−3 at 485°C. The electron mobility increased with increasing growth temperature, reaching values of 3630 and 21800 cm2/Vs at 300 and 77K, respectively. The photoluminescence was found to depend strongly on the growth temperature. Excitonic luminescence was detected only for growth temperatures above 465°C. The intensity of the band edge emission is comparable to that of the acceptor related emission for layers grown at 465°C. At 485°C, the band-edge recombination is dominant and the acceptor related emission is barely observable. As the growth temperature increased from 465 to 485°C, the full width at half maximum of the bound exciton peak decreased from 6.8 to 3.5 meV at 14K. This trend was consistent with the decrease in the impurity concentration deduced from the Hall effect measurements. [ABSTRACT FROM AUTHOR]

We report an anomalous Zn surface diffusion in InP during annealing of ohmic contact structures containing Zn. A Pd/Zn/Pd contact was used to demonstrate this phenomenon. Electrical properties of the contact were monitored to corroborate this anomalous surface diffusion. Cross-sectional scanning electron microscopy was also used to delineate the Zn diffusion front lines. It was found that the Zn surface lateral diffusion can extend ≥50 µm for samples annealed at 500°C or higher temperatures. Close attention should be paid to this anomalous lateral surface diffusion during fabrication of devices using Zn-contained ohmic contacts. [ABSTRACT FROM AUTHOR]

Low temperature photoluminescence (PL) has been used to characterize InAlAs/InGaAs/InP heterojunction field-effect transistor (HFET) structure material. A phenomenological lineshape model has been applied to the PL spectrum to derive energy levels and the position of the Fermi-energy and hence the channel carrier concentration. The data is compared with results from low-temperature Hall and Shubnikov-de Hans (SdH) measurements, and fit with a charge-control model of the conduction band. Values for the sheet density are derived from PL for channel-doped structures where SdH measurements are difficult. Changes in the quantum well symmetry through variations in the dopant distribution are shown to be reflected in the PL lineshape. [ABSTRACT FROM AUTHOR]

Depositing Pd or Au on InP at cryogenic substrate temperatures has previously been found to significantly increase the barrier height of the resulting Schottky diode. In this work, cross-sectional transmission electron microscopy was used to determine the structural differences between metal/semiconductor (MS) interfaces formed at 300K (RT) and at 77K (LT). In the Pd/lnP case, RT samples exhibited a thick amorphous interaction layer at the MS interface, while LT samples only had a thin phosphorous-rich interfacial layer. However, in the Au/InP case, no amorphous interlayers were observed in any of the samples. Instead, a small amount of Au was found to extend into the InP lattice in the RT case which was not present in LT samples. The thermal stability of the barrier height was studied as well. LT Au/lnP samples were found to exhibit a distinct barrier height shift when annealed at 200°C which was linked to a grain coarsening in the polycrystalline Au layer at this temperature. X-ray diffraction was used to verify changes in the polycrystalline metal's average grain size. We conclude that a significant reduction in the interaction between the deposited metal and InP was responsible for the greatly enhanced barrier height observed in LT interfaces. [ABSTRACT FROM AUTHOR]

We have discovered what appears to be a unique contact system for use on p-type InP. The new contacts provide low resistance contact to p-InP without the violent metallurgical intermixing that would normally take place between the emitter material and the contact metallization during the contact sintering process. With this new contact system, which is composed of a combination of Ag and Zn, it is possible, for the first time, to make low resistance ohmic contact directly to a shallow junction p/n InP device without destroying the device while doing so. Specific contact resistivity values in the low 10 Ω-cm range are readily achieved. After a description of the new system, we suggest possible mechanisms to explain the observed behavior. [ABSTRACT FROM AUTHOR]

Rare earth-and transition metal-doped thin films of InP, InGaAs, and InGaAsP were grown by liquid phase epitaxy and evaluated for use in integrated electro-optical and magneto-optical applications, such as waveguides and Faraday rotators. The films were lattice matched to (100) InP substrates, and the transition metal (Mn) and rare earth (Gd, Eu, and Er) doping concentra-tions were between 2.6 × 10 and 1.5 × 10 cm. The chemical profiles were generally found to be homogeneous by SIMS, although in more highly doped films the rare earths were observed to segregate toward the interfaces. The undoped films were n-type, and the net carrier concentrations in the rare earth-doped (Gd, Eu, Er) films were decreased by an order of magnitude. The Mn-doped films were p-type. Optically, the rare earth dopants were observed to raise the refractive index of the layers at 632.8 nm, and subsequent waveguiding in doped InP layers was observed at 1.3 μm. Although the Faraday rotations of our materials were much less than that of well known oxides, such as yttrium iron garnet, they were sufficient for device applications, and our materials can be much more easily integrated with InP OEIC devices. For example, a 1 cm waveguide would provide the large rotation (45°) required in isolator applica-tions. [ABSTRACT FROM AUTHOR]

Using surface photo-absorption spectra, we established a phase diagram of the surface chemical-bonding structure for the P-stabilized surface in InP metalorganic vapor phase epitaxy as a function of substrate temperature and PH partial pressure. At 550°C and PH partial pressures of 10 and 30 Pa, the surface is (2 × 4)-like consisting of P dimers having a bond axis parallel to [110]. As the substrate temperature decreases and the PH partial pressure increases, amorphous P species start to adsorb excessively on (2×4)-like P dimer surface. A c(4 × 4)-like surface was not observed. From InP growth experiments for each P surface phase, we found that, to obtain high-quality InP epitaxial layers, excess P adsorption should be suppressed by minimizing the formation of native defects. [ABSTRACT FROM AUTHOR]

Cu diffusion was carried out in p-InP at 300°C for one hour followed by 600°C for one minute. High photoconductivity (I/I = 2.6 × 10 at 200K) was observed in this sample. Information about Cu related deep levels was obtained from dark conductivity, photoconductivity and its spectral response. A Cu related photoluminescence (PL) band was observed at 1.216 eV and its line-shape and line-width analysis carried out. The configuration coordinate diagram of the band was calculated and showed small lattice relaxation. In n-InP Cu diffusion at 650°C for two hours resulted in two PL bands at 1.20 and 1.01 eV. The former was similar to the 1.216 eV band in p-InP. The PL of the 1.01 eV band was also studied in detail and the corresponding configuration coordinate diagram derived. The parameters of the Cu related bands obtained from the line-shape and line-width analysis are compared with those reported due to Mn and Fe in InP. [ABSTRACT FROM AUTHOR]

It has been demonstrated that a highly doped (Si:3 × 10 cm) triple capping layer consisting of n−InGaAs, n−InAlAs, and n-InGaAs can remarkably reduce the parasitic source resistance in InP-based high electron mobility transistors (HEMTs). The analysis of the source resistance revealed that the resistance element at the n−InGaAs/un−InAlAs/un-InGaAs channel heterointerfaces was as large as 70% of the source resis-tance when nonalloyed ohmic electrodes were used. The highly doped triple capping layer reduces the resistance contribution of vertical conduction between the capping layer and 2DEG channel. A low source resistance of 0.57 Ωmm and a low contact resistivity of 3 × 10 Ωcm were obtained for the HEMTs with the highly doped triple capping layer, which were 60% lower and one order of magnitude smaller than those for the HEMTs with a conventional single capping layer doped 5 × 10 cm, respectively. These values were also 70 and 30% lower than those for the HEMTs with a highly doped (3 × 10 cm) single capping layer, respectively. The low source resistance brings high peak extrinsic transconduc-tance of 1 S/mm for a device with 0.4 μm long gate, which was 42% higher than the previously reported HEMTs with the same gate length. [ABSTRACT FROM AUTHOR]

The effects of interfacial layers with high impurity concentration on the properties of homoepitaxial InP layers have been studied by far-infrared (FIR) magnetoabsorption, in addition to dc mobility, Hall effect, and photoluminescence (PL) measurements. The layers are grown by organometallic vapor phase epitaxy with trimethylindium and tertiarybutylphosphine. Impurity absorption as well as cyclotron resonance is observed in the FIR measurements. Variations in the intensity of the resonance signals and the mobilities obtained from the linewidths of the cyclotron resonance are interpreted by a double layer model, i.e. a bulk layer with an interfacial layer. Carrier concentrations, dc mobilities, and PL intensities of both bound excitons and free excitons are also explained by the model. [ABSTRACT FROM AUTHOR]

In situ remote plasma processes consisting of removal of native oxide due to hydrogen (H) plasma, surface modification due to phosphine (PH) plasma and deposition of phosphorus nitride (PN) films due to decomposition of PH by nitrogen (N) plasma have been developed. The insulating PN film with optical bandgap of 5.3 eV and electrical resistivity of 3.7× 10 Ωcm is obtained by remote plasma chemical vapor deposition. Au/PN/InP tunneling metal-insulator-semiconductor (MIS) type Schottky junction is formed by the in situ multiprocess. The effective barrier height is estimated to be as high as 0.83 eV. Enhancement of the effective barrier height is due to both effects of the MIS structure and unpinning of the surface Fermi level. [ABSTRACT FROM AUTHOR]

Thin layers of chemical bath deposited cadmium sulfide were used to improve the surface and interface properties of InP and its latticed-matched III-V compounds. X-ray photoelectron spectroscopy indicates chemical reduction of surface oxides and the prevention of subsequent group III or V oxide formation. Photoluminescence spectra, measured between 1.0 and 1.3 μm, indicate a dramatic reduction in phosphorus vacancies following CdS treatment. Metalinsulator-semiconductor capacitors fabricated on n-type InP substrates with CdS interlayers display near-ideal quasi-static response and interface-state densities in the low 10/eVcm range. Thin CdS layers were used to passivate the surface of InAlAs/InGaAs high electron mobility transistors (HEMTs) and metal-semiconductor-metal (MSM)photodetectors.AfterCdS treatment, Schottky diode barrier heights of 0.6 eV were regularly obtained. For HEMTs, drain-togate current ratios of 8 × 10 were observed after CdS treatment. For a new backside illuminated MSM design, the dark current of CdS-treated samples was reduced three orders of magnitude to below 1 nA. [ABSTRACT FROM AUTHOR]

The sulfur chemical bonding state on (NH)S-treated InP(100) surfaces has been studied by S 1 s core-level photoelectron measurements using synchrotron radiation soft x-rays. The change in the sulfur chemical bonding states caused by rinsing with water and annealing in vacuum after the (NH)S-treatment was observed clearly in the S 1 s spectra. Four kinds of sulfur bonding states were resolved in the S 1 s spectrum of the as-treated surface. Only one sulfur bonding state was detected on the surfaces with and without the water rinse after annealing, indicating that the InP surfaces were terminated by the S-In bond. The effect of rinsing the (NH)S-treated InP surface is discussed by comparison with the (NH)S-treated GaAs surface. [ABSTRACT FROM AUTHOR]

Etching of InP using a beam of PC1 is demonstrated in a standard gas source molecular beam epitaxy machine. The principle of an atomic layer accurate end-point detection technique using in-situ reflection high energy electron diffrac-tion is described and used to study the kinetics of PCl etching. The etch rate is found proportional to the PCI fluence and weakly dependent on the substrate temperature. The morphology of etched surfaces and the etch rate uniformity is compatible with the regrowth of high quality InGaAsP active structures and with the realization of etch and regrowth sequences controlled at the nm scale. Etch profiles at mask edges are defined by nearly perfect crystallographic facets with a very limited mask undercut (≈100 nm) due to the beam nature of the etching technique. [ABSTRACT FROM AUTHOR]

The addition of a thin Ni layer has improved the surface morphology of Al/ n-InP contacts which show an enhanced Schottky barrier height (SBH) after rapid thermal annealing. In order to determine the optimum thickness of the insertion Ni layer, we have fabricated a unique sample in which the thickness of the insertion Ni layer tapered off in space. The improvement of the surface morphol-ogy as well as the SBH enhancement were realized by inserting 35 nm Ni layer annealed at rather low temperatures (around 450°C). The solid-phase reaction between Ni and InP might play an important role in the low-temperature formation of A1P which was responsible for the SBH enhancement. [ABSTRACT FROM AUTHOR]

We report for the first time, a surface passivation technique for InP/InGaAs heterojunction bipolar transistors that is suitable for optoelectronic integrated circuits. The combination of buffered hydrofluoric acid with high temperature annealing of the surface causes significant increase of the gain at low input currents. Using this technique, transistors were integrated with photodetectors and other optoelectronic devices and had current gains as high as 400 even at nanoampere base currents. [ABSTRACT FROM AUTHOR]

Chlorine auto-doping phenomenon was found for the first time in InP epitaxial growth by using a PCl/InP/H system. Chlorine atoms act as a donor in the epitaxial layer and the carrier concentration is dependent on the facet of InP substrate. The carrier concentration of the InP layer on ( 111)B facet was over 10 times higher than that on (111)A substrate. [ABSTRACT FROM AUTHOR]

In this study, the use of a novel phosphorous precursor for low pressure metalorganic vapor phase epitaxy (LP-MOVPE) application has been investigated. Ditertiarybutyl phosphine ((CH)-P-H, DitBuPH) as substitute for the standardly used hydrid gas phosphine (PH) promises apart from strongly reduced toxicity due to the reduction of P-H bonds, an enhancement in cracking efficiency as well as a reduction in growth temperature. Layer quality has been examined by means of optical and scanning electron microscopy (SEM), temperature-dependent van der Pauw Hall as well as photoluminescence (PL) measurements. Uncompensated n-type InP-layers (1.0 x 1.5 cm; 59600 cmVs) at 77K) are realized using DitBuPH in combination with commercial TMIn. All results are compared with those obtained by using PH and commercial tertiarybutyl phosphine (TBP) as P-source, respectively. [ABSTRACT FROM AUTHOR]

We have investigated the selective growth of pnp- InP by metalorganic chemical vapor deposition (MOCVD) around mesas. The mesas were formed by reactiveion-etching using SiO masks having various patterns. The patterns include stripes along different crystallographic orientations, Y-bifurcations, and X-crossings. The behavior of the growth, and that of the mass transport before the growth, were found to depend remarkably on the crystallographic direction of the mesa stripe. The most notable mass transport, which transforms a nearly vertical mesa wall to a sloped one, was observed for a stripe misoriented by about 30° from the [011] direction. The growth was observed to proceed preferentially on the sloped planes, planarizing the crystal surface, for a mesa stripe directed between the [011] and [010] directions. However, for the stripe direction near [01-1], the growth was observed to creep up a nearly vertical plane on the mesa wall, and sloped planes are reluctant to form. Selective growth with sufficient planarity has been obtained for various waveguides including the Y-bifurcations and the X-crossings, which are used as the waveguide components in photonic integrated circuits, when the stripes are almost along the [011] direction. [ABSTRACT FROM AUTHOR]

Temporally resolved selective regrowth of InP around reactive ion etched [110] and [-110] directional mesas is studied by hydride vapor phase epitaxy at the growth temperatures of 600, 650, 685, and 700°C. The regrowth profiles are strikingly different depending upon the mesa orientation. The results are interpreted by invoking the difference in the bonding configurations of these mesas as well as the growth facility in a direction leading to the largest reduction of dangling bonds under the growth conditions. Various emerging planes during regrowth are identified and are hhl planes with initial values of 1/h ≤ 3 but ≥ 3 as the planarization is approached. Initial lateral growth defined as the growth away from the mesa at half of its height in the very first minute is a decreasing function of temperature when plotted as Arrhenius curves. Such a behavior is attributed to the exothermicity of the reaction and to an enhanced pyrolysis of PH to P. The lateral growth rate is much larger than that on the planar substrate. This should be taken into account when regrowth of a doped layer (e.g. InP:Fe or InP:Zn) is carried out to fabricate a buried heterostructure device since the dopant concentration can be very much lower than the one optimized on the planar substrates. [ABSTRACT FROM AUTHOR]

A comparative study has been carried out regarding selective embedding growth of InP by metalorganic chemical vapor deposition (MOCVD) around dry-etched mesas, using two types of reactors: a conventional horizontal type and a highspeed rotating-susceptor type. In the case of the conventional horizontal-type MOCVD, overgrowth on the mask was observed when the growth temperature was low (600°C). On the other hand, an almost planar grown surface without such overgrowth was achieved by using the high-speed rotating-susceptor MOCVD for a wide range of growth temperatures, especially even at a low growth temperature of 580°C. Regarding the high-speed rotating-susceptor MOCVD, we have also investigated the effects of dopants on the growth behaviors and have found a remarkable difference between n-type S-doped and p-type Zn-doped InP in the growth behaviors. The mechanism for suppressing overgrowth in case of the high-speed rotating-susceptor MOCVD, as well as the cause for the different effects between the dopants, are discussed. [ABSTRACT FROM AUTHOR]

We have developed a modified liquid encapsulated Czochralski (LEC) method with thermal baffles, by which low dislocation density InP crystals can be grown. In this method, thermal baffles are set on top of the crucible in order to suppress the gas convection and thus to improve the temperature gradient in the LEC furnace. However, the dislocation densities depend not only on the temperature gradient but also on other growth conditions, such as crystal/crucible rotation rates, cooling rates, and the thickness of the pBN crucible. Since the rotation rate affects the solid/liquid interface shape, it is an important factor for the reduction of dislocation densities. By optimizing these conditions, for Sn and Fe doped InP crystals, average dislocation densities less than 5 x 10 cm can be achieved. Dislocation free (DF) S and Zn doped InP crystals can also be grown if the carrier concentration is more than 3 x 1018 cm. The DF crystals become rectangular in shape. [ABSTRACT FROM AUTHOR]

Crystal quality of 2′ Φ S doped InP substrates grown by the conventional liquid encapsulated Czochralski method was studied by the photoluminescence mapping technique and double crystal x-ray diffraction method. Dark currents of InGaAs/InP PIN-photodiodes (PIN-PDs) fabricated on them showed the existence of an anomaly at the center of the substrate. Photoluminescence intensity abruptly decreased at the center of the substrate. An abnormal curvature of the lattice plane was found at the center of the substrate by the double crystal x-ray diffraction measurement. We discuss the correlation between crystal quality of the substrate and dark currents of PIN-PDs. [ABSTRACT FROM AUTHOR]