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Due to the ultrawide bandgap (4.9 eV), high carrier mobility (300 cm 2 V − 1 s − 1 ), and high thermal stability, β − Ga 2 O 3 can be a potential candidate for high-temperature thermoelectric materials. However, the intrinsically high thermal conductivity may hinder its application for thermoelectric conversion. In this work, porous β − Ga 2 O 3 was prepared by the solvothermal method together with spark plasma sintering technology. Positron lifetime measurement and N 2 adsorption confirm the introduction of pores by adding sucrose in the sample preparation. The sucrose-derived β − Ga 2 O 3 sintered at a relatively low temperature of 600 ° C remains highly porous, which results in an extremely low thermal conductivity of 0.45 W m − 1 K − 1 at room temperature, and it further decreases to 0.29 W m − 1 K − 1 at 600 ° C. This is the lowest thermal conductivity for β − Ga 2 O 3 reported so far. Our work provides an avenue to reduce the thermal conductivity for β − Ga 2 O 3 and is believed to be widely applicable to many other thermoelectric materials. [ABSTRACT FROM AUTHOR]

Persistent photocapacitance (PPC) was observed in β-(Al0.14Ga0.84)2O3/n+Ga2O3 heterojunctions at low temperatures. The effect is seen in capacitance-frequency measurements under illumination and in admittance spectra after illumination. In the latter case, the capacitance versus frequency curve after illumination returned to its dark values only at temperatures between 225 and 275 K. Prominent hole-trap-like peaks in optical deep level transient spectroscopy (ODLTS) near 130 K were attributed to quenching with temperature of the PPC effect. The phenomena were assigned to electrons being excited from deep traps in the (Al0.14Ga0.86)2O3 barrier into the two-dimensional electron gas (2DEG) in the Ga2O3 substrate. The reverse process then involves excitation of non-equilibrium electrons in the 2DEG back into the ternary barrier layer and subsequent re-capture by the host deep traps. The effective barrier height for this recovery process was ∼0.2 eV, as estimated from ODLTS measurements. The spectral dependence of the effect suggests the presence of deep traps with optical ionization thresholds near 1 eV and ∼2.3 eV. The shift of the threshold voltage necessary to deplete the 2DEG as a function of the photon energy during illumination at room temperature indicates that the most prominent centers in the barrier have an optical ionization energy near 2.3 eV and a sheet density of ∼1012 cm−2. In microcathodoluminescence (MCL) spectra of the heterojunction, a blue shift by 0.2 eV of the MCL band near 3.1 eV dominant in the substrate and the emergence of a weak MCL peak near 4.8 eV were observed. Electron beam induced current measurements point to the presence of small local areas where the 2DEG formation is handicapped due to Al composition variations or to defects. [ABSTRACT FROM AUTHOR]

A mono-layer of ZnO nanoparticles (NPs), each of which does not mostly overlap with one another, was formed on the surface of a silica glass by implantation with 60 keV Zn+ ions and subsequent thermal oxidation. Then, the sample was irradiated with swift heavy ions (SHIs) of 200 MeV Xe14+ ions in the fluence range of 1 × 1011–5 × 1013 ions/cm2. The X-ray diffraction intensity of the {002} peak from ZnO NPs shows a steep drop to 67% of the unirradiated value at the fluence of 1 × 1012 ions/cm2 but maintains almost the same value up to 50 times higher fluence of 5 × 1013 ions/cm2. The behavior could be ascribed to high susceptibility of this material ZnO for recrystallization in the cooling stage of the thermal spike: While damage remains at the central region of SHI impact, recrystallization is induced in large surrounding regions. The interplay between the damage generation in the core regions and the recovery in the surrounding regions reaches a dynamical equilibrium at the fluence exceeding 1 × 1012 ions/cm2. While it is known that free excitons are sensitive to defect registration, the free exciton photoluminescence (PL) with 20% of the unirradiated intensity still survives up to the highest fluence 5 × 1013 ions/cm2. The stable tolerance of this material in optical absorption and PL against SHI irradiation could be attractive for applications. [ABSTRACT FROM AUTHOR]

The spatial distribution of electron-hole pair generation in β-Ga2O3 as a function of scanning electron microscope (SEM) beam energy has been calculated by a Monte Carlo method. This spatial distribution is then used to obtain the diffusion length of charge carriers in high-quality epitaxial Ga2O3 films from the dependence of the electron beam induced current (EBIC) collection efficiency on the accelerating voltage of a SEM. The experimental results show, contrary to earlier theory, that holes are mobile in β-Ga2O3 and to a large extent determine the diffusion length of charge carriers. Diffusion lengths in the range 350–400 nm are determined for the as-grown Ga2O3, while processes like exposing the samples to proton irradiation essentially halve this value, showing the role of point defects in controlling minority carrier transport. The pitfalls related to using other popular EBIC-based methods assuming a point-like excitation function are demonstrated. Since the point defect type and the concentration in currently available Ga2O3 are dependent on the growth method and the doping concentration, accurate methods of diffusion length determination are critical to obtain quantitative comparisons of material quality. [ABSTRACT FROM AUTHOR]

β-Ga2O3 rectifiers fabricated on lightly doped epitaxial layers on bulk substrates were exposed to CF4 plasmas. This produced a significant decrease in Schottky barrier height relative to unexposed control diodes (0.68 eV compared to 1.22 eV) and degradation in ideality factor (2.95 versus 1.01 for the control diodes). High levels of F (>1022 cm−3) were detected in the near-surface region by Secondary Ion Mass Spectrometry. The diffusion of fluorine into the Ga2O3 was thermally activated with an activation energy of 1.24 eV. Subsequent annealing in the range 350–400 °C brought recovery of the diode characteristics and an increase in barrier height to a value larger than in the unexposed control diodes (1.36 eV). Approximately 70% of the initial F was removed from the Ga2O3 by 400 °C, with the surface outgas rate also being thermally activated with an activation energy of 1.23 eV. Very good fits to the experimental data were obtained by integrating physics of the outdiffusion mechanisms into the Florida Object Oriented Process Simulator code and assuming that the outgas rate from the surface was mediated through fluorine molecule formation. The fluorine molecule forward reaction rate had an activation energy of 1.24 eV, while the reversal rate of this reaction had an activation energy of 0.34 eV. The net carrier density in the drift region of the rectifiers decreased after CF4 exposure and annealing at 400 °C. The data are consistent with a model in which near-surface plasma-induced damage creates degraded Schottky barrier characteristics, but as the samples are annealed, this damage is removed, leaving the compensation effect of Si donors by F− ions. The barrier lowering and then enhancement are due to the interplay between surface defects and the chemical effects of the fluorine. [ABSTRACT FROM AUTHOR]

Ohmic contacts to n-SiC, a semiconductor material, were studied.

A new study investigates the electrical properties of W contacts to p- and n-GaN.

Ti+, O+, Fe+ and Cr+ were found to produce defect levels when implanted in n- and p-type GaN.

An analysis of the role of extended and point defects and key impurities such as C, O, and H, on the optical and electrical properties of GaN was conducted. The rapid development and commercialization of blue and green light-emitting diodes (LEDs) and the achievement of long-lifetime laser diodes was followed by realization of UV photodetectors and several different electronic devices. Continued rapid development in the areas of LEDs, laser diodes, microwave and digital electronic devices, UV detectors ad high voltage unipolar and bipolar devices is expected as an improved understanding of the defect and impurity issues in these materials evolve.

Ion milling rates of III-V nitrides have been measured as a function of Ar(+) ion beam. Ion channeling, AES and SEM enable the analysis of the influence of nitride surfaces. Ion milling rates for these samples are smaller than those of GaAs and InP. Ion milling has no influence on the surface morphology of the nitride. All these nitrides exhibit more back-scattering for Ar(+) energies up to 500 eV.

Implant isolation schemes, specifically used for dense and greatly doped III-V devices such as quantum well lasers and heterojunction bipolar transistors (HBT) generate extended defects, situated particularly at areas of strain. Diffusion of keV H+, MeV O+ and F+ ions is analyzed. MeV O+ ions are used for isolating strained quantum well lasers which work at 0.98 micrometers and keV H+ and F+ ions are used for isolating GaAs/AlGaAs HBTs.

Si+ and Be+ ions, implanted into InGaAsP grown lattice, matched to InP by molecular beam epitaxy, are experimented upon to determine the electrical activation characteristics as a function of ion dose, annealing time and annealing temperature. For both Si and Be ions, maximum doping concentrations were obtained with the electrical activation energies of 0.58 and 0.39 electron volts. High resistance layers for isolation is produced by multiple energy implant of F or H ions. The maximum sheet resistance for the InGAsP is determined for F implants by annealing at 450 degrees centigrade. Electron cyclotron resonance CH4/H2/Ar discharges at low direct (dc) basis is used in the determination of the smooth, anisotropic dry etching of the InGaASp.

The use of tri-isobutylgallium (TIBG) and tri-isopropylgallium (TIPG) for enhancing the metalorganic molecular beam epitaxial growth of InGaP was investigated. The result showed that the incorporation rate of carbon decreased as the temperature increased. The measured lattice constant varied linearly with the flow. The band gap varied discontinuously with the lattice constant.

A study was conducted on the effectivity of using mega electronvolt (MeV) O+ ion implantation for isolation of GaAs/AlGaAs heterojunction bipolar transistors (HBTs). High sheet resistances were observed in the GaAs epitaxial layers. The presence of a residual conductivity was attributed to hopping processes with small activation energies. The study shows that MeV can effectively produce HBTs with optimal direct current properties. MeV application also proved to be clear due to the thick layer stuctures involved.

High quality Pnp heterojunction bipolar transistors can be obtained through the use of carbon: aluminum gallium arsenic and tin doping from tetraethylin during metalorganic molecular beam epitaxy growth. Large area devices with gains of 45 at a base doping level of 1.5 x 10 (super 9) cm (super -3) were demonstrated. The slight doping levels were obtained with carbon and tin reducing the parasitic resistances in the transistor.

A single-energy, MeV implant isolation method for thick II-V semiconductor device structures is presented. The process greatly simplifies conventional keV implant isolation, which uses ten separate ion energies in isolating HBT structures. Damage profile is constant over the primary part of the ions range. The damage usually found with the MeV ions end of range can be kept secure in the underlying substrate.

A study measured minority electron diffusion length in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. Irradiation with a low energy (5kV0 electron beam resulted in an increase of diffusion length with a similar activation energy (219 plusmn 8 meV).

Ion beam irradiation is a powerful method to fabricate and tailor the nanostructured surface of materials. Nanorods on the surface of single crystal rutile TiO2 were formed by N+ ion irradiation. The dependence of nanorod morphology on ion fluence and energy was elaborated. With increasing ion fluence, nanopores grow in one direction perpendicular to the surface and burst finally to form nanorods. The length of nanorods increases with increasing ion energy under same fluence. The development of the nanorod structure is originated from the formation of the nanopores while N2 bubbles and aggregation of vacancies were responsible for the formation of nanopores and nanorods. Combining C+ ion irradiation and post-irradiation annealing experiments, two qualitative models are proposed to explain the formation mechanism of these nanorods. [ABSTRACT FROM AUTHOR]

The drain current fluctuation of ungated AlGaN/GaN high electron mobility transistors (HEMTs) measured in different fluids at a drain-source voltage of 0.5 V was investigated. The HEMTs with metal on the gate region showed good current stability in deionized water, while a large fluctuation in drain current was observed for HEMTs without gate metal. The fluctuation in drain current for the HEMTs without gate metal was observed and calculated as standard deviation from a real-time measurement in air, deionized water, ethanol, dimethyl sulfoxide, ethylene glycol, 1,2-butanediol, and glycerol. At room temperature, the fluctuation in drain current for the HEMTs without gate metal was found to be relevant to the dipole moment and the viscosity of the liquids. A liquid with a larger viscosity showed a smaller fluctuation in drain current. The viscosity-dependent fluctuation of the drain current was ascribed to the Brownian motions of the liquid molecules, which induced a variation in the surface dipole of the gate region. This study uncovers the causes of the fluctuation in drain current of HEMTs in fluids. The results show that the AlGaN/GaN HEMTs may be used as sensors to measure the viscosity of liquids within a certain range of viscosity. [ABSTRACT FROM AUTHOR]

The white light luminescence is observed from the silica slides implanted by sequential Si+ and C+ ions or only by C+ ions followed by thermal annealing. In the photoluminescence (PL) spectra, their white emissions cover the whole visible spectral range from 350 to 800 nm. The influence of thermal annealing on the PL of the implanted samples was studied. The microstructural and optical analysis allow us to figure out the origin of the white light emission, which is mainly attributed to the emission of graphite like C clusters although the contributions from the emissions of the Si and SiC nanocrystals are also included. Compared to the white light emission of C+ implanted sample, the white light emission of Si+/C+ implanted sample has higher thermal stability. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) and optically detected magnetic resonance (ODMR) techniques are utilized to examine the effects of P implantation and post-implantation annealing on defect formation in ZnO single crystals. From ODMR, the main defects created by ion implantation include oxygen and zinc vacancies as a well as a deep donor labeled as PD. The formation of the PD defect is likely promoted by the presence of P as it could only be detected in the P-containing ZnO. The VO and PD centers are found to exhibit low thermal stability and can be annealed out at 800 °C. On the other hand, a new set of defects, such as Z, T, and D* centers, is detected after annealing. Based on measured spectral dependences of the ODMR signals, the VO, VZn, and PD centers are shown to participate in spin-dependent recombination processes related to red emissions, whereas the Z, T, and D* centers are involved in radiative recombination over a wide spectral range of 1.55-2.5 eV. From the PL measurements, combined effects of implantation and annealing also lead to appearance of a new PL band peaking at ∼3.156 eV, likely due to donor-acceptor-pair recombination. The formation of the involved deep acceptor is concluded to be facilitated by the presence of P. [ABSTRACT FROM AUTHOR]

The thermal and chemical stability of potential dielectrics for GaN-based devices in a GaN metal organic chemical vapor deposition (MOCVD) environment is investigated, and their suitability for use as a gate dielectric and as a regrowth mask for the selective area growth of GaN is discussed. Thin films of MgO, Sc2O3, and Sc2O3/MgO were grown by molecular beam epitaxy on GaN/sapphire substrates and then annealed in a MOCVD reactor under GaN growth conditions except for the lack of trimethylgallium. All films were processed into metal-oxide-semiconductor diodes and were characterized before and after being annealed using atomic force microscopy, x-ray reflectivity, x-ray photoelectron spectroscopy, current-voltage (I-V), and capacitance-voltage (C-V) measurements. The Gibbs free energy of all possible reactions was calculated, and their probability and possible influence on the characterization results is examined. After being annealed, the atomic force microscopy of the oxide films showed some degree of roughening for all of them. Despite the surface roughening, all the oxide films examined showed potential for use as a regrowth mask. The MOCVD anneal caused the electrical properties of the MgO film to degrade considerably, and the Sc2O3 films were unable to be electrically characterized after annealing due to shorting, which is believed to be caused by the formation of a ScN layer on the surface. The effect of the thickness of the Sc2O3 cap for MgO films was investigated. The characterization results indicate that the Sc2O3 film dissolved into MgO during annealing and that a ScN film did not form on the surface. Of all the oxide films examined in this study, the Sc2O3/MgO stack with the thinner Sc2O3 cap exhibited the greatest stability with respect to its electrical properties. [ABSTRACT FROM AUTHOR]

Chemical sensors can be used to analyze a wide variety of environmental and biological gases and liquids and may need to be able to selectively detect a target analyte. Different methods, including gas chromatography, chemiluminescence, selected ion flow tube, and mass spectroscopy, have been used to measure biomarkers. These methods show variable results in terms of sensitivity for some applications and may not meet the requirements for a handheld biosensor. A promising sensing technology utilizes AlGaN/GaN high electron mobility transistors (HEMTs). HEMT structures have been developed for use in microwave power amplifiers due to their high two dimensional electron gas (2DEG) mobility and saturation velocity. The conducting 2DEG channel of AlGaN/GaN HEMTs is very close to the surface and extremely sensitive to adsorption of analytes. HEMT sensors can be used for detecting gases, ions, pH values, proteins, and DNA. In this paper we review recent progress on functionalizing the surface of HEMTs for specific detection of glucose, kidney marker injury molecules, prostate cancer, and other common substances of interest in the biomedical field. [ABSTRACT FROM AUTHOR]

The Zn1-xCoxO and Al-doped Zn1-xCoxO nanowires have been synthesized by the water-assistance reactive vapor deposition method. No Co precipitates appeared in the both kinds of ZnO nanowires according to the results observed by high-resolution transmission electron microscope, x-ray diffraction, and electron energy-loss spectroscopy, revealing that the magnetism of the ZnO nanowires was independent of the Co precipitates. The Al-doped Zn1-xCoxO nanowires show much stronger ferromagnetism than Zn1-xCoxO nanowires in the temperature range of 4–350 K. It is believed that the ferromagnetism in Zn1-xCoxO nanowires could be enhanced by Al doping to introduce donor carriers. Moreover, a multiple mechanism for the ferromagnetism of Al-doped Zn1-xCoxO nanowires is discussed. [ABSTRACT FROM AUTHOR]

The transport properties of as-deposited and rapid thermal annealed phosphorus-doped ZnO films grown by pulsed laser deposition are reported. As-grown ZnO:P samples showed n-type characteristics, presumably due to the formation of antisite PZn defects. Rapid thermal annealing yielded a carrier-type conversion from n- to p-type for the ZnO:P films grown at ∼700 °C; samples grown at substantially lower or higher temperatures tended to remain n-type even after the thermal annealing process. The properties and behavior of the n-to-p conversion are most consistent with the formation of PZn-2VZn as the active acceptor state. Variable magnetic field Hall measurements confirmed the p-type behavior. Phosphorus doping concentrations in the range of 0.5-1.0 at. % were considered, with evidence for P segregation in the higher phosphorus concentrations. [ABSTRACT FROM AUTHOR]

The performance of AlGaN/GaN heterostructure field-effect transistors (HFETs) with either uncapped surfaces or with low-temperature (LT) GaN or SiO2 or SiNx as gate insulators is reported. The sheet carrier concentrations of AlGaN/GaN HFETs with any of these surface insulating layers are similar to each other and in each case about 50% higher than that in an AlGaN/GaN HFET with a free surface. This result is consistent with the insulator layers providing passivation of surface states that cause the depletion of the channel layer. Due to the closer lattice match with the AlGaN surface layer, the HFET with a LT-GaN layer as the gate insulator shows the best dc and rf device performance, demonstrating that this material is an effective insulator for nitride electronic devices. [ABSTRACT FROM AUTHOR]

The synthesis, structure, and optical properties of one-dimensional heteroepitaxial cored (Zn,Mg)O semiconductor nanowires grown by a catalyst-driven molecular beam epitaxy technique are discussed. The structures form spontaneously in a Zn, Mg and O2/O3 flux, consisting of a single crystal, Zn-rich Zn1-xMgxO(x<0.02) core encased by an epitaxial Zn1-yMgyO(y>0.02) sheath. High resolution Z-contrast scanning transmission electron microscopy shows core diameters as small as 4 nm. The cored structure forms spontaneously under constant flux due to a bimodal growth mechanism in which the core forms via bulk like vapor-liquid-solid growth, while the outer sheath grows as a heteroepitaxial layer. Temperature-dependent photoluminescence shows a slight blueshift in the near band edge peak, which is attributed to a few percent Mg doping in the nanoscale ZnO core. The catalyst-driven molecular beam epitaxy technique provides for site-specific nanorod growth on arbitrary substrates. [ABSTRACT FROM AUTHOR]

Investigates the effects of hydrogen on the electrical and optical properties of p-gallium arsenide. Incorporation of hydrogen into the material; Result of the hydrogen passivation of acceptors rather than of increased compensation by donor centers; Increase in the concentration of 0.4 eV hole traps by hydrogen plasma treatment.

The effects of hydrogen plasma treatment on high-quality bulk n-ZnO crystals were studied. It is shown that after plasma exposure at 200 °C for 0.5 h the hydrogen penetrates into the material down to about 20 µm and shows concentrations close to 10[sup 17] cm[sup -3] in that region. The incorporation of this hydrogen coincides with an increase in the shallow donor concentration to about the same level as the concentration of hydrogen. In contrast to that in most other semiconductor materials, hydrogen plasma treatment of ZnO is shown to increase the concentration of the already existing electron and hole traps and to introduce electron traps near 0.55 eV, earlier observed in proton irradiated samples. The effect is at least partially due to the surface damage caused by plasma exposure. Despite this increase in the density of deep traps, the luminescence intensity in the near band-edge region is shown to increase down to the depth corresponding to the hydrogen penetration depth in the material. [ABSTRACT FROM AUTHOR]

Recent advances in the theory and experimental realization of ferromagnetic semiconductors give hope that a new generation of microelectronic devices based on the spin degree of freedom of the electron can be developed. This review focuses primarily on promising candidate materials (such as GaN, GaP and ZnO) in which there is already a technology base and a fairly good understanding of the basic electrical and optical properties. The introduction of Mn into these and other materials under the right conditions is found to produce ferromagnetism near or above room temperature. There are a number of other potential dopant ions that could be employed (such as Fe, Ni, Co, Cr) as suggested by theory [see, for example, Sato and Katayama-Yoshida, Jpn. J. Appl. Phys., Part 2 39, L555 (2000)]. Growth of these ferromagnetic materials by thin film techniques, such as molecular beam epitaxy or pulsed laser deposition, provides excellent control of the dopant concentration and the ability to grow single-phase layers. The mechanism for the observed magnetic behavior is complex and appears to depend on a number of factors, including Mn-Mn spacing, and carrier density and type. For example, in a simple Ruderman-Kittel-Kasuya-Yosida carrier-mediated exchange mechanism, the free-carrier/Mn ion interaction can be either ferromagnetic or antiferromagnetic depending on the separation of the Mn ions. Potential applications for ferromagnetic semiconductors and oxides include electrically controlled magnetic sensors and actuators, high-density ultralow-power memory and logic, spin-polarized light emitters for optical encoding, advanced optical switches and modulators and devices with integrated magnetic, electronic and optical functionality. [ABSTRACT FROM AUTHOR]

Optical absorption spectra, microcathodoluminescence (MCL) spectra, and electrical properties of GaMnN films grown by molecular-beam epitaxy with Mn concentration in the range of 3 to 10 at. % were studied. Optical absorption and MCL spectra show the presence of strong bands corresponding to the transition from the Mn acceptors near E[SUBc] - 2 eV to the conduction band. The other strong band observed in MCL measurements was the blue band peaked near 2.9 eV and associated with the transition from the valence band to deep donors with a level near E[SUBc] - 0.5 eV. All GaMnN samples were shown to be lightly n-type which suggests close self-compensation of the Mn acceptors by some native defect donors. A plausible scenario is that such compensating donors could be due to nitrogen vacancies and that the E[SUBc] - 0.5 eV donor defects are complexes between the Mn acceptors and the nitrogen vacancy donors. [ABSTRACT FROM AUTHOR]

Optical transmission spectra, microcathodoluminescence spectra, capacitance-voltage and capacitance-frequency curves, temperature dependence of resistivity and deep level spectra with both electrical and optical injection were measured on n-GaN samples implanted with high doses of Mn (3 × 10[sup 16] and 4 × 10[sup 16] cm[sup -2]) and Co (4 &times ; 10[sup 16] cm[sup -2]). From optical transmission it was found that Mn forms a deep acceptor near Ev + 1.8 eV while the Co acceptor is about 0.1 eV deeper. In addition, Mn and Co form complexes with native defects and these complexes are deep electron traps with a level near Ec-0.5 eV. Such complexes are most likely responsible for a strong blue luminescence band with energy near 2.9 eV. Adjacent to the implanted region a defect region about 1 µm deep is formed, most likely by out-diffusion of point defects from the implanted zone during the 700°C annealing used to partially remove the radiation damage. This region is characterized by a high density of electron traps at Ec-0.25 eV and Ec-0.7 eV and hole traps at Ev + 0.2 eV, Ev + 0.35 eV and Ev + 0.45 eV. [ABSTRACT FROM AUTHOR]

Multi-quantum-well GaN/InGaN heterojunction diodes prepared by metalorganic chemical vapor deposition on sapphire showed effects of strong tunneling in their I–V characteristics. The space charge region was shown to be located in the GaN/InGaN superlattice (SL). The injection of moderately high forward currents through the structure for several hours enhanced the overall tunneling through the structure and facilitated faster tunneling between the layers in the GaN/InGaN SL. These results may have relevance to the aging characteristics of light-emitting diodes under bias. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The diode ideality factor, reverse breakdown voltage, and forward current characteristic were used to measure the effect on electric performance of GaAs rectifiers deposited with thin films of SiN[sub x]. Over a broad range of deposition conditions there were minimal changes (<10%) in breakdown voltage and the cause was hydrogen passivation of Si dopants in the GaAs. Ion-induced damage did not appear to play a significant role in the results. The ideality factors and forward leakage currents were essentially unchanged by the SiN[sub x] deposition indicating that the plasma exposure did not create defects states around the periphery of the Schottky contact. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The morphology of ultrathin AlN/GaN high electron mobility transistors without or with TiAlNiAu Ohmic contacts is examined by using transmission electron microscopy and associated analytical methods. The contact inclusion (CI) density has increased with increasing annealing temperature but the lowest specific contact resistivity is obtained for structures annealed at 850 [degree]C and the AlN layers have remained intact in dislocation-free areas of all samples.

The transport properties of as-deposited and rapid thermal annealed phosphorus-doped ZnO films grown by pulsed laser deposition are analyzed. The properties of these films are used for extrapolating the behavior of the phosphorus dopant in the process-dependent creation of effective acceptor states.

The performance of AlGaN/GaN heterostructure field-effect transistors (HFETs) with either uncapped surfaces or with low-temperature (LT) GaN or SiO2 or SiN(sub x) as gate insulators is reported. The result is consistent with the insulator layers providing passivation of surface states that cause the depletion of the channel layer.

The synthesis, structure, and optical properties of one-dimensional heteroepitaxial cored (Zn, Mg) O semiconductor nanowires grown by a catalyst-driven molecular beam epitaxy technique are discussed. The temperature-dependent photoluminescence shows a slight blueshift in the near band edge peak, which is attributed to a few percent Mg doping in the nanoscale ZnO core.

Describes the simultaneous formation of buried external collector and extrinsic base regions in gallium arsenide/AlGaAs heterojunction bipolar transistor (HBT) structures by co-implantation of beryllium+ together with oxygen+ or hydrogen+ ions. Effect of high annealing temperature on beryllium (Be) activation; Reduction of the base-collector capacitance and the associated changes in parasitic resistances; Redistribution of the Be and the residual disorder in the HBT structure.

Discusses a study on the improved growth conditions by molecular-beam epitaxy and fabrication of state-of-the-art aluminum gallium arsenide (GaAs)/GaAs selectively doped heterostructure transistors and ring oscillators on silicon substrates. Effects of substrate misorientation on 2DEG properties; Properties of the two-dimensional electron gas; Schottky diodes characteristics and doping profiles on undoped gallium arsenide-on-silicon.

Examines the electrical activation characteristics of silicon and beryllium ions implanted into indium-gallium arsenide-phosphrus grown lattice matched to indium-phosphorus metalorganic molecular beam epitaxy as a function of ion dose, annealing time and temperature. Attainment of maximum doping concentrations of the ions; Activation energies of the ions; Use of multiple energy fluorine and hydrogen ions to produce high resistance layers.

Presents a study that introduced atomic hydrogen by two methods into gallium arsenide (GaAs) layers epitaxially grown on silicon substrates. Correlation of the amount of hydrogen incorporated during plasma exposures with the amount of initial disorder in the GaAs layer; Use of current-voltage measurements in titanium-platinum-gold Schottky diode structures; Effects of the defects in the GaAs layer.

Discusses a study that reported the electrical measurements on structures by doping barriers of a gallium arsenide quantum well. Details on the Hall-effect and capacitance-voltage measurements; Use of gas-source molecular-beam epitaxy methods in growing the quantum well transistors; Result of the study.