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In this paper, a leaky-mode directional coupler based on grating-assisted coupling between a semiconductor subwaveguide and a polymer subwaveguide is experimentally demonstrated at wavelengths near 1310 nm. The grating is fabricated at the interface between the semiconductor and polymer materials. The grating period satisfies the phase-matching condition for power exchange between the two nonsynchronous subwaveguides. Experimental and theoretical results show coupling from the semiconductor subwaveguide to the polymer subwaveguide as a function of excitation wavelength.

The combination of resonant-tunneling diodes and heterostructure field-effect transistors provides a versatile technology for implementing microwave digital and mixed-signal applications. Here we demonstrate and characterize the first monolithic flash analog-to-digital converter (ADC) in this technology. The first-pass ADC achieved 2.7 effective bits at 2 gigasamples per second (Gsps) for a 220-MHz input signal. The one-bit quantizer achieved a single-tone spurious free dynamic range greater than 40 dB at 2 Gsps for a 220-MHz single-tone input with dithering.

The use of silicon tetrabromide and carbon tetrabromide for n- and p-type doping respectively of In 0.53 Ga 0.47 As and InP materials grown by metalorganic molecular beam epitaxy (MOMBE) has been investigated. Controllable n-type doping concentrations from 1 × 10 16 cm −3 to 6 × 10 19 cm −3 have been obtained in InP using SiBr 4 and tertiarybutylphosphine (TBP). Silicon doping concentrations from n = 1 × 10 16 cm −3 to 1 × 10 19 cm −3 have been obtained in InGaAs grown using tertiarybutylarsine (TBA). Slightly lower concentrations were obtained when using tris-dimethylaminoarsenic (DMAAs) as the arsenic source. A memory effect has been observed when transitioning from heavily to lightly doped layers, and is attributed to accumulated SiBr 4 evaporating from uncooled surfaces in the growth chamber. Carbon doping of InGaAs to carrier concentrations of 8 × 10 19 cm −3 have been obtained with CBr 4 and TBA; however, significantly lower p-type doping levels are obtained when DMAAs is used as the arsenic source. We attribute this behavior to the DMAAs decomposition products reacting with carbon on the wafer surface. Secondary ion mass spectroscopy (SIMS) profiling of heavily Si- and C-doped materials indicates that bromine incorporation is below the detection level of our instrument ( 15 cm −3 ). These dopant sources have been used for the growth of InP-based heterojunction bipolar transistor (HBT) structures. Both single- and double-heterojunction device structures have been produced with f t of 69–91 GHz and f max of 163–166 GHz, which are comparable to the same structures grown using conventional dopant sources.

A lattice‐matched InP/InGaAs resonant tunneling diode is studied by scanning tunneling microscopy and spectroscopy. Results show both a structural and chemical asymmetry between the normal and inverted interfaces. The inverted (InP on InGaAs) interface is considerably rougher than the normal interface, and the frequency components of the roughness at both interfaces have been calculated. Additionally, certain images show enhanced and reduced state densities at the normal and inverted interfaces, respectively, which is most likely due to dissimilar bonding types at the interfaces. Spectroscopic observations of evanescent valence‐band states tailing into the InP barrier allow for direct measurement of the valence‐band offset.

We review the recent developments of GaInP/GaAs heterojunction bipolar transistors (HBTs) used for microwave power, low noise, linear amplification and high temperature applications. Special attention is paid in the comparison of the GaInP HBT results with the more conventional AlGaAs HBTs. The material and processing advantages, as well as the electronic and thermal properties of GaInP are described.

This paper describes the use of tertiarylbutylarsine (TBA) and tertiarylbutylphosphine (TBP) as replacements for arsine and phosphine in MOMBE/CBE for the production of device structures with state-of-the-art performance. The growth system used for this work is based on the use of elemental group-III and dopant sources, and embryos thermal crackers for the low pressure precraking of TBA and TBP. Device structures fabricated in the In 0.48 Ga 0.52 P/GaAs material system include single- and double-heterojunction bipolar transistor (SHBTs and DHBTs)

A vertical field-effect resonant tunneling transistor is demonstrated consisting of a triple-barrier, double-well resonant tunneling diode (3bRTD) that can be depleted by the action of side gates. The 3bRTD features a double peak current-voltage characteristic in which the second valley current is less than the first valley current. Combination of the resonant tunneling transistor and a constant current load is shown to yield both binary and ternary logic and memory functions. >

The Stillinger-Weber interatomic potential for silicon was used to simulate the atomic arrangement at the emergence points of a/2〈110〉 perfect edge dislocations at a free surface. Results indicate step heights are comparable in magnitude vectors parallel to the surface can produced steps at the surface. The resulting step heights are comparable in magnitude with the steps which would be created if these dislocations were dissociated into Shockley partials. As a result, step source activation from these dislocations is possible without dissociation. The origin of the steps can be rationalized in terms of the Poisson expansion and contraction owing to relaxation of the compressive and tensile stress fields of the edge dislocations at a free surface.

Negative differential resistance (NDR) has been observed at room temperature in GaInP/GaAs double-heterojunction bipolar transistors (DHBTs). Both the common-emitter and common-base current-voltage characteristics and their magnetic field dependence have been studied to confirm that the observed NDR is due to resonant tunneling. The collector-base voltages at which the collector current resonances occur are calculated and are consistent with the measured values. The devices exhibit an offset voltage of 57 mV and saturation voltage of >

GaInP/GaAs heterojunction bipolar transistors (HBTs) and both graded and abrupt AlGaAs/GaAs HBTs were fabricated. A total of 20 wafers were analyzed. Comparisons of the experimental results establish that the dominant carrier transport mechanism in GaInP/GaAs HBTs is the carrier diffusion through the base layer. This suggests that the conduction-band barrier across the GaInP/GaAs emitter-base junction is so small that the barrier spike does not affect the carrier transport. This result differs from other published results which, by studying device structures other than HBTs, determined the conduction band barrier to be as large as approximately 50% of the bandgap difference. The findings of the present investigation, however, agree well with another published work which also examined an HBT structure. The difference between these works is discussed. >

This paper describes a study on the use of thermally cracked tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBA) with elemental Ga and In sources for the metalorganic molecular beam epitaxy (MOMBE) growth of the In 0.53 Ga 0.47 As/InP and In 0.48 Ga 0.52 P/GaAs materials systems. Modulated beam mass spectroscopy was used to characterize the thermal decomposition of these Group-V metal alkyls. Results indicate that As 2 and P 2 are the dominant growth species produced when cracker temperatures greater than 700°C are used. These conditions result in high quality epitaxial layers with essentially zero oval defects (less than l/cm 2 ) despite the use of elemental Group-Ill sources. Results of doping and heterointerface studies indicate that these Group-V precursors are suitable replacements for hydride sources. Application of these precursors for device structure growth including heterojunction bipolar transistors (HBTs) and resonant tunneling diodes (RTDs) is also described.

Bulk single crystals of InxGa1-xAs (0.01

We have fabricated arrays of resonant tunneling diodes based on InP substrates for exposure at room temperature with fluences of 3 MeV protons up to 7×1014 H+/cm2. Proton fluences below about 1×1013 cm−2 have little effect on the resonant tunneling diode but higher fluences decrease the peak current and increase the valley current. We find that proton-induced changes in the operating parameters are qualitatively similar to the effects of doping the wells.

The mechanisms associated with the replication and annihilation of dislocations during the homoepitaxial growth of indium phosphide layers by liquid phase epitaxy have been investigated. Two distinct situations develop during the growth of homoepitaxial layers on dislocated substrates: the Burgers vector of a substrate dislocation is either inclined or parallel to the growth surface. The replication of dislocations which have their Burger's vector parallel to the growth surface has been studied by cross-sectional transmission electron microscopy. Results suggest that perfect dislocations are incorporated into epitaxial layers without an increased separation between Shockley partials in contrast to observations in silicon homoepitaxial layers. In addition, their orientation is observed to change so as to align themselves parallel to the growth direction. In contrast, dislocations whose Burgers' vectors are inclined to the surface propagate in the usual 60° configuration. The annihilation of dislocations has been studied using X-ray topography and cross-sectional transmission electron microscopy. Results indicate that the annihilation that is observed in the absence of stress can be accounted for by chance impingement of dislocations during growth. This is facilitated by the climb of closely spaced dislocations. The effects of stress due to non-stoichiometric growth and isoelectronic doping have also been studied and have been found to be detrimental to the overall perfection of epitaxial layers.

A 50-nW standby power compound semiconductor tunneling-based static random access memory SRAM (TSRAM) cell is demonstrated by combining ultralow current-density resonant-tunneling diodes (RTDs) and heterostructure field-effect transistors (HFETs) in one integrated process on an InP substrate. This power represents over two orders of magnitude improvement over previous III-V static memory cells. By increasing the number of vertically integrated RTD's we obtain a 100 nW tri-state memory cell. The cell concept applies to any material system in which low current-density negative differential resistance devices are available.

A planar integrated lateral double barrier heterostructure resonant tunneling diode is demonstrated. Resonances in the current–voltage (I–V) characteristics are observed that have peak‐to‐valley current ratios as high as 3.5 at 4.2 K and are attributed to resonant tunneling in a two‐dimensional/one‐dimensional/two‐dimensional system. The device structure consists of a lateral double barrier heterostructure embedded in an InP/InGaAs/InP modulation‐doped field‐effect transistor structure. The lateral heterostructure uses InP barriers and an InGaAs quantum well fabricated by epitaxial etch and regrowth techniques. This device and fabrication process forms the basis for lateral resonant tunneling transistors.

We report for the first time the Ka-band power performance of InP/InGaAs/InP DHBTs. A 2/spl times/10 /spl mu/m/sup 2/ common-emitter transistor delivered a continuous wave (CW) output power of 19.1 mW (1.91 W/mm power density), an associated gain of 5.3 dB, and a power-added efficiency (PAE) of 35.5% at 30 GHz. The maximum output power density was 2.34 W/mm and the peak associated gain was 6.6 dB. Under common-base operation, the maximum associated gain increased to 15.2 dB, but the maximum output power density and peak PAE dropped to 1.91 W/mm and 24.5%, respectively, at the same frequency.

We report experimental and theoretical evidence for electrostatic lateral confinement induced by a nanoprobe. The lateral confinement is manifest as oscillations of the differential conductance of a near‐surface resonant‐tunneling heterostructure in air at room temperature.

We propose and demonstrate a new resonant-tunneling diode (RTD) based memory cell in which bits are stacked vertically while their addressing requires only two physical contacts to the vertically integrated RTDs (VIRTDs). Toward meeting the ultra low static power requirements we have developed record low current density (down to 0.16 A/cm2) InP based RTDs with 300 K peak-to-valley current ratios (PVCRs) ranging from 2.9 to 18.

Continued down-scaling of electron devices in integrated circuits in order to achieve higher density eventually results in electron devices in which quantum effects play a significant role. These quantum effects can be exploited and used to increase the functionality of electronic devices and circuits resulting in high-density (multi-valued) logic and memory functions. The lateral resonant tunneling diode and transistor are two quantum effect devices that are well suited for this task and are also ideal for planar integration. A planar lateral double barrier heterostructure is demonstrated here for the first time. Resonances in the I-V characteristics are observed that have peak to valley current ratios as high as 3.5 at 4.2 K and are attributed to resonant tunneling in a 2D/1D/2D system. The InP substrate based device structure consists of an InP/lnGaAs/InP MODFET structure within which a lateral double barrier heterostructure, consisting of InP barriers and InGaAs well and contacts, has been integrated by etch and regrowth techniques. This demonstration opens the way for the fabrication of the lateral resonant tunneling transistor.

Significant progress has been made over the past few years in both the technology and microwave performance of InP-based heterojunction bipolar transistors (HBTs). Emphasis has, however, been placed mainly on transistor performance. Other critical issues have largely been ignored, including the influence of InGaAs on device thermal resistance, the role of base-collector leakage current, and the phenomenon of thermal instability. This paper first briefly reviews recent microwave results achieved to date and then investigates the aforementioned critical issues that affect their use in microwave applications.

The authors report the first co-integration of resonant tunneling and heterojunction bipolar transistors. Both transistors are produced from a single epitaxial growth by metalorganic molecular beam epitaxy, on InP substrates. The fabrication process yields 9- mu m/sup 2/-emitter resonant tunneling bipolar transistors (RTBTs) operating at room temperature with peak-to-valley current ratios (PVRs) in the common-emitter transistor configuration, exceeding 70, at a resonant peak current density of 10 kA/cm/sup 2/, and a differential current gain at resonance of 19. The breakdown voltage of the In/sub 0.53/Ga/sub 0.47/As-InP base/collector junction, V/sub CBO/, is 4.2 V, which is sufficient for logic function demonstrations. Co-integrated 9- mu m/sup 2/-emitter double heterojunction bipolar transistors (DHBTs) with low collector/emitter offset voltage, 200 mV, and DC current gain as high as 32 are also obtained. On-wafer S-parameter measurements of the current gain cutoff frequency (f/sub T/) and the maximum frequency of oscillation (f/sub max/) yielded f/sub T/ and f/sub max/ values of 11 and 21 GHz for the RTBT and 59 and 43 GHz for the HBT, respectively. >

The first resonant-tunneling hot-electron transistor (RHET) EXCLUSIVE-NOR integrated circuit that operates at room temperature is demonstrated. The XNOR circuit consisting of a single resonant-tunneling transistor and four thin-film resistors, exhibits a 500-mV output voltage swing between the high- and low-logic levels when biased with a 1.8-V supply. The transistor, which features a novel InGaP collector barrier, has a peak current density of 4*10/sup 4/ A-cm/sup -2/, a common-base transfer coefficient of 0.9, and a peak-to-valley current ratio of 10:1 when operated in a common-emitter mode. >

Very-high-performance common-emitter InP/InGaAs single heterojunction bipolar transistors (HBTs) grown by metalorganic molecular beam epitaxy (MOMBE) are reported. They exhibit a maximum oscillation frequency (f/sub T/) of 180 GHz at a current density of 1*10/sup 5/ A/cm/sup 2/. this corresponds to an (R/sub B/C/sub BC/)/sub eff/=f/sub T//(8 pi f/sup 2//sub max/) delay time of 0.12 ps, which is the smallest value every reported for common-emitter InP/InGaAs HBTs. The devices have 11 mu m/sup 2/ total emitter area and exhibit current gain values up to 100 at zero base-collector bias voltage. The breakdown voltage of these devices is high with measured BV/sub CEO/ and BV/sub CEO/ of 8 and 17 V, respectively. >

The combination of resonant tunneling diodes (RTDs) and heterostructure field-effect transistors (HFETs) provides a versatile technology for implementing microwave digital and mixed-signal applications. Here we demonstrate the first monolithic flash RTD/HFET analog-to-digital converter (ADC). The first pass ADC achieved 2.7 effective bits at 2 GSps. The one bit quantizer achieved a single tone spurious free dynamic range (SFDR) of greater than 40 dB at 2 GSps for a 220 MHz single tone input with dithering.

Gas-source molecular beam epitaxy (GSMBE) has been developed into a useful tool for the growth of both optical and electronic device structures. In this paper, we report on the use of tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) in GSMBE for the growth of electronic device structures with state-of-the-art performance. Device structures based on both the In0.48Ga0.52P/GaAs and In0.53Ga 0.47As/InP lattice matched materials systems are described. The GSMBE system is based on the use of elemental Group-rn sources and employs thermal crackers for precracking TBA and TBP. Dopant sources include both elemental (Sn and Be) and vapor (CBr4 and SiBr4) sources. Device structures fabricated in the In0.48Ga0.52P/GaAs materials system include single- and double- heterojunction bipolar transistors (SHBTs and DHBTs). Device structures fabricated in the In0.53Ga0.47As/InP materials system include SHBTs, DHBTs, heterojunction field effect transistors (HFETs), and both planar and lateral resonant tunneling diodes (RTDs.) Vertically integrated HFET and multi-RTD heterostructures for high speed logic/memory are also described.

Resonant tunneling transistors can perform more logic per transistor than conventional transistors. By exploiting their unique characteristic, circuit functional density and speed can be increased without changing the lithographic design rule. In addition, resonant tunneling transistors, in which the control electrode directly modulates the carrier transport, scale to smaller dimensions than conventional transistors. In this paper, the measured negative differential resistance and transconductance characteristics of several resonant tunneling transistors are described.

Lateral resonant tunneling devices that employ heterostructure charge barriers are candidates to replace complementary metal–oxide–semiconductor devices as the basic device type that will drive integrated circuit technology in the next century. We present progress in lateral resonant tunneling device technology including the first lateral resonant tunneling transistor that has heterostructure barriers to be fabricated with planar processing techniques. The devices produced to date are limited to cryogenic operation; however, they do demonstrate that lateral resonant tunneling devices can be fabricated with etch and regrowth techniques and suggest the possibility of an integrated circuit technology that may be scaled down to less than 10 nm and would operate at room temperature.

Summary form only given. It is demonstrated that 300-K operation of an InGaAs-based HET (hot-electron transistor) can be achieved by further increasing the electron injection energy in combination with the use of a wide-bandgap base-collector isolation barrier. The characteristics of a device consisting of an InAlAs emitter, a 10-AA AlAs tunnel-barrier positioned at the emitter-base heterojunction, a 400-AA n+ InGaAs base region, and a 2500-AA InAlGaAs collector barrier are reported. The injected electrons are transported across the base region with over 80% efficiency, as measured in a common-base configuration. The maximum common-emitter current gain in this nonoptimized transistor is nearly four with an f/sub T/ of over 40 GHz and a base-collector breakdown voltage of 1.5 V. A systematic study of RHET (resonant tunneling HET) injector and collection properties indicates that the HET can operate at room temperature with a current gain on the order of 100. 300-K operation of a single-RHET, exclusive-NOR integrated circuit that is similar in design to the one demonstrated at 77 K by N. Yokoyama et al. (1985) is also shown. >

The use of reflection mass spectrometry (REMS) for in situ monitoring of group III flux transients during molecular‐beam epitaxial growth is reported. Normal shutter closure caused effusion cell heating which resulted in flux overshoots of up to 30%. The variation of the magnitude and time constant of the overshoot, as a function of group III material and shutter closed time, was determined for our Riber 2300 system. It was verified that the observed REMS transients corresponds to growth transients using photoluminescence and transmission electron microscopy analysis of GaAs/AlGaAs and InGaAs/InAlAs multiple quantum well (MQW) structures. Flux transient correction during GaAs/AlGaAs MQW growth was accomplished by ramping the temperature of the Ga effusion cell, based on our previous analysis of the transients.

The first resonant tunnelling bipolar transistor integrated circuits operating at room temperature are demonstrated. The circuits are composed of cointegrated resonant tunnelling bipolar transistors and double heterojunction bipolar transistors based on InP substrates. Both a three-transistor XNOR and a seven-transistor XOR logic gate have been demonstrated using a 3 V power supply.

Summary form only given. The authors report very-high-performance InP/InGaAs double-heterojunction bipolar transistors (DHBTs) with low output conductance and high breakdown voltage of at least 5.5 V at high current densities, with measured BV/sub CEO/ and BV/sub CBO/ of >7.5 V and 10.6 V, respectively. The 11 mu m/sup 2/ devices exhibited f/sub T/ of 134 GHz and f/sub max/ of 113 GHz at V/sub CE/=1.57 V and I/sub C/=16.22 mA. The epitaxial structure was grown by metal-organic molecular beam epitaxy (MOMBE) using tertiarybutylarsine and tertiarybutylphosphine as the group-V sources. >

Superlattice photovoltaic waveguide detectors have been fabricated and tested with a strained-layer superlattice active region of four alternating atomic monolayers of Ge and Si. The infra-red spectral response extends to 1.4 mu m. The peak of the optical response is shifted toward the visible relative to Ge-Si alloy detectors of a similar average composition. >

We report an improved tunneling-based SRAM (TSRAM) cell design using symmetric low current density InGaAs/InAlAs/AlAs/InAs resonant-tunneling diodes (RTD's). The new design eliminates an interconnect compared to the previous record low 50 nW TSRAM cell demonstrated with asymmetric low current density RTDs and heterostructure field-effect transistors (HFETs) in our InP-based integrated process. The simplified cell has 4/spl times/ smaller area than III-V FET-only SRAM cells at the same design rule. We also investigate experimentally and theoretically the mechanism for reduced peak-to-valley current ratios for very low current density (/spl sim/1 A/cm/sup 2/) RTDs which affects TSRAM cell standby power.