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Double-side molecular beam epitaxial growth on a thick LEC-grown semi-insulating (SI) GaAs wafer has been used to demonstrate a novel high power optothyristor for pulsed power-switching applications. The optothyristor has a P/sup +/N-SI-PN/sup +/ thyristor-like structure with the capital P and N standing for the wider bandgap optical window material, AlGaAs, and the SI standing for a 650 /spl mu/m SI-GaAs substrate. With the "insertion" of the SI-GaAs bulk material into the conventional P/sup +/NPN/sup +/ thyristor structure and the use of wider bandgap AlGaAs, the device has achieved a record high performance compared to the existing GaAs or AlGaAs/GaAs based epitaxial thyristors. The performance of the optothyristors under forward bias has been characterized, including 1) the low field dynamic current-voltage characteristics to show post-triggering carrier injections. 2) the switched-current waveforms with varying device blocking voltage and from which the turn-on speed di/dt is determined, and 3) the dependence of the switched-current amplitude on the laser triggering position. >

GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures (≈200°C) exhibits the desired properties of a high-speed photoconductor: high resistivity, high mobility, high dielectric-breakdown strength, and subpicosecond carrier lifetime. The unique material properties are related to the excess arsenic content in the MBE grown epilayers. Due to the combination of the above properties, dramatically improved performance has been observed in photoconductive detectors and correlators using submicron spaced electrodes. In addition to GaAs, low-temperature growth of InxGa1−xAs alloys also leads to the incorporation of excess arsenic in the layers, and therefore this material system exhibits many beneficial photoconductor properties as well. In particular, the lattice-mismatched growth of LT-InxGa1−xAs on GaAs appears to be the most suited for high-speed detector applications in the near-infrared wavelength range used in optical communications. The material issues and the photodetector characteristics required to optimize their performance are discussed.

The subpicosecond carrier lifetime of an unannealed molecular beam epitaxial layer of GaAs grown at ∼210°C has been demonstrated between 10 and 290K through optoelectronic switching and all-optical pump-probe measurements. The low room-temperature resistivity of the as-grown layers, believed to arise from hopping conductivity through defect sites, has been observed to increase as the sample temperature was lowered, allowing ultrafast switching measurements to be performed using the low-temperature-as-grown GaAs as a photoconductive element. After illumination by 100 femtosecond optical pulses, photogenerated carriers in the sample have rapidly relaxed, returning the material to its high-resistivity state in less than 1 ps. This indicates that the precipitates present in post-annealed samples are not required for the fast relaxation of photoexcited carriers in low-temperature-grown GaAs. Ultrafast switching measurements on a post-annealed version of the GaAs film also resulted in the generation of similar, 0.6 ps full width at half maximum pulses.

The reverse‐biased performance of a molecular‐beam‐epitaxy‐grown high‐power optothyristor has been systematically characterized for pulsed power‐switching applications. The device has a P+N‐SI‐PN+ thyristor‐like structure with the bipolar junctions formed by AlGaAs. The semi‐insulating (SI) GaAs used is liquid‐encapsulated‐Czochralski grown, undoped, and 650 μm in thickness. It is found that the reverse‐biased optothyristor can be triggered by a light‐emitting diode operated at 10−5 W, and miniature semiconductor lasers can trigger the switch with 132 A current using only a 1‐mm‐diam optical aperture. The reverse switching di/dt and the maximum peak current are reported as a function of blocking voltage. The effects of bipolar junctions on both sides of the SI‐GaAs are also reported by comparing the bulk photoconductive current with the optothyristor switched current. It is shown that a laser beam of 0.05 μJ can be used to trigger on and switch about the same current as a 0.3 μJ laser beam, suggesting the...

High electron mobility transistors (HEMTs) with single-quantum-well active layers composed of pseudomorphic InGaAs on GaAs and InP substrates have yielded substantial performance enhancements relative to their lattice-matched equivalents. The higher cut-off frequencies possessed by these devices have enabled new applications to be realized in the millimeter wave spectrum which are not feasible with lattice-matched HEMTs. Also, the devices are beginning to displace GaAs field effect transistors in the microwave spectrum as a result of higher gain and power-added efficiency inherent to the pseudomorphic devices. These developments in transistors and parallel developments in other strained layer material systems and devices have been paced by a resurgence in research and development in the materials science and engineering of strained epitaxial layers.

The authors report the first successful demonstration of a metal-semiconductor-metal photodetector (MSMPD) fabricated on low-temperature InGaAs grown on GaAs by molecular beam epitaxy (MBE) for long-wavelength fiber optic applications. Interdigitated MSMPDs with finger widths and spacings of 0.2, 0.5, 1.0, and 2.0 mu m were tested using a femtosecond pulsed laser and high-speed electrooptic sampling. A FWHM pulsed response of 2 and 1.3 ps was measured for low-temperature In/sub 0.25/Ga/sub 0.75/As and In/sub 0.35/Ga/sub 0.65/As, respectively. The latter is the fastest response reported to data for a photodetector capable of detection to wavelengths as long as 1.3 mu m. >

A heterojunction-based optothyristor has been fabricated and tested with biasing field intensity up to 34 kV/cm for pulsed power applications. The reverse-biased optothyristor can even be triggered by a light-emitting diode (LED) of a few microwatts power, and more than 500 times reduction in the required LED power for triggering has been observed when compared to bulk photoconductive switches. The optothyristor, however, does not turn on under similar triggering conditions if bias polarity is changed. The sensitive optical gating of the reverse-biased optothyristor is explained. The turn-on delay time under reverse bias has been found to be inversely proportional to the square root of the LED power. The possibility of improving the switching efficiency by superimposing the laser pulse on a constant lower level background illumination has been demonstrated. >

The electrical and optical properties of AlGaAs grown by metalorganic molecular‐beam epitaxy using triethylaluminum, tri‐isobutylaluminum, and trimethylamine‐alane are compared. It is found that tri‐isobutylaluminum yields the lowest residual carbon incorporation in the layers (Na − Nd = 4 × 1015 cm−3) and the highest electron and hole mobilities. Photoluminescence spectra for the higher‐quality AlGaAs, grown using TiBAl, show excitonic luminescence. However, this luminescence appears to be defect related.

Migration-enhanced epitaxy (MEE) has been employed successfully to grow high quality GaAs buffer and InGaAs channel layers at 300°C. Planar-doped GaAs MESFETs with a thin MEE GaAs buffer layer have been fabricated for comparison with devices using conventional MBE buffers. Our preliminary data indicate that the MEE buffer alternative offers reduced side-gating effect, lower output conductance, better pinchoff characteristics and higher channel current. RF measurements indicate an improvement in output power density, gain and efficiency for the MEE-buffered MESFETs. High electron mobility transistor (HEMT) devices fabricated on modulation-doped pseudomorphic AlGaAs/InGaAs/GaAs heterostructures with a thin MEE buffer layer yield higher transconductance (gm), transistor gain, and unity current gain cutoff frequency (ƒT) compared to the conventional MBE-buffered devices. Moreover, HEMT devices with an MEE InGaAs channel grown at 300°C achieve comparable gm and ƒT to those with a conventional MBE channel grown at ∼500°C. Critical layer thickness of InGaAs on GaAs using the MEE method, under the growth conditions reported here, is found to exceed that of MBE.

This paper describes the operating principles and performance of a gas handling system, which was designed specifically for the metalorganic molecular beam epitaxy (MOMBE) growth of III–V compound semiconductors. The system employs three-parameter control (carrier flow, reagent vapor pressure and bubbler pressure) to deliver a stable and reproducible flow of each metalorganic reagent. This approach permits a very wide range of reagent flux to be conveniently accessed. This flux can be exactly predicted, using a modification to the simple theoretical expression that has been used previously. Data for the repeated growth of GaAs FET structures show that the growth rate is stable and has an excellent day-to-day reproducibility. A novel compensated vent/run gas switching system is used to eliminate pressure transients that can otherwise occur when switching the reagent gases in and out of the MOMBE growth chamber. This system has been used for the growth of GaAs and AlGaAs and we show that the growth rate stabilizes within one monolayer during a change of III–V composition. This allows us to grow heterojunctions with monolayer abruptness as determined by RHEED oscillations and photoluminescence studies of narrow quantum well samples.

Growth and characterization results are presented for pseudomorphic high electron mobility transistor structures with InxGa1-xAs single quantum well and GaAs(h 1)In x Ga1−x As(h 2) thin strained superlattice active layers where 0.25≤x ≤ 0.4. All of the samples were grown by molecular beam epitaxy. Hall effect at 77 K, photoluminescence at 2 K, in-situ reflection high energy electron diffraction, and transmission electron microscopy measurements are discussed. Critical layer thickness measurements are compared with the Matthews-Blakeslee theory. Photoluminescence transition energies are compared with a self-consistent solution to Schrodinger’s and Poisson’s equations.

Very low-noise 0.15- mu m gate-length W-band In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As/InP lattice-matched HEMTs are discussed. A maximum extrinsic transconductance of 1300 mS/mm has been measured for the device. At 18 GHz, a noise figure of 0.3 dB with an associated gain of 17.2 dB was measured. The device also exhibited a minimum noise figure of 1.4 dB with 6.6-dB associated gain at 93 GHz. A maximum available gain of 12.6 dB at 95 GHz, corresponding to a maximum frequency of oscillation, f/sub max/, of 405 GHz (-6-dB/octave extrapolation) in the device was measured. These are the best device results yet reported. These results clearly demonstrate the potential of the InP-based HEMTs for low-noise applications, at least up to 100 GHz. >

The microwave characterization of 0.25- mu m gate-length MODFETs at 300 and 77 K is reported. Microwave S-parameter measurements of MODFETs from 0.45 to 20 GHz were used to extract their HF equivalent network parameters. After allowing for the parasitic gate and drain-to-gate feedback capacitances, the intrinsic unity-current gain frequency was determined. Using a theoretical model, the effective carrier saturation velocity and average velocity ( nu /sub av/) were obtained for the conventional AlGaAs/GaAs, the pseudomorphic AlGaAs/InGaAs/GaAs, and lattice-matched InAlAs/InGaAs/InAlAs on InP samples at 300 K and 77 K. The extracted values of nu /sub a/ range from 0.82*10/sup 7/ cm/s to 3.84*10/sup 7/ cm/s, respectively, depending on the type of MODFET and operating temperature. These high values of nu /sub av/ indicate that the velocity overshoot effect is present in the devices tested. >

Quarter-micron InAlAs/InGaAs planar-doped HEMTs (high-electron-mobility transistors) lattice-matched to InP have exhibited state-of-the-art noise and gain performance at frequencies up to 94 GHz. Minimum noise figures of 0.5, 1.2, and 2.1 dB have been measured at 18, 60, and 94 GHz, respectively. Small signal gains as high as 15.4 and 12.0 dB have been obtained at 63 and 95 GHz, respectively. Using 0.25 mu m InP-based HEMTs, a V-band three-stage amplifier yields an average noise figure of 3.0 dB with a gain of 22.0 +or-0.2 dB from 60 to 65 GHz at W-band, a two-stage amplifier exhibits a noise figure of 4.5 dB with a gain of 10.2 dB at 90.4 GHz, and a three-stage amplifier shows a noise figure of 4.8 dB with a gain of 15.0 dB at 90.4 GHz. It is concluded that these results clearly show the great potential of InP-based HEMTs for high-performance millimeter-wave low-noise receiver applications. >

Doped-channel, 0.25- mu m-gate-length, InGaAs pseudomorphic HEMTs (high electron mobility transistors) have been developed which exhibit state-of-the-art power performance at millimeter-wave frequencies, with output power density of 0.93 W/mm and power-added efficiency of 41% at 44 GHz. Using these devices, two Q-band hybrid power amplifiers have been developed. A two-stage design has produced 108 mW output power gain with 9.5 dB and 26.5% power-added efficiency. A three-stage design produced 251 mW output power with 13.6 dB of gain and 26.8% power-added efficiency. The peak efficiency of the three-state amplifier was 31.3% when biased differently. The linear gain of these amplifiers was 12 and 20 dB respectively. It is concluded that these amplifiers are an attractive alternative for designers of future millimeter-wave transmitters. >

A 0.15- mu m-gate-length double-heterojunction pseudomorphic HEMT (high electron mobility transistor) that exhibits state-of-the-art power and noise performance is reported. Power results include record power-added efficiencies of 51%, 41% and 23% at 35, 60 and 94 GHz, respectively, and output powers of 139 mW at 60 GHz and 57 mW at 94 GHz. Measured minimum noise figures of 0.55 dB at 18 GHz and 1.8 dB at 60 GHz are reported. It is suggested that because of its demonstrated performance and continued rapid rate of improvement, the pseudomorphic HEMT should be the preferred transistor for a number of millimeter-wave applications, used either as a discrete device in high-performance hybrid amplifiers or integrated into GaAs-based MMICs (monolithic microwave integrated circuits). >

The authors report the development of short gate-length (0.15-0.25- mu m) HEMTs (high-electron-mobility transistors) with state-of-the-art noise and power performance. The three families of HEMTs-conventional GaAs/AlGaAs, pseudomorphic, and InP-based-are described and compared. The InP HEMTs offer the lowest noise figure: device noise figures of 0.3 dB at 18 GHz and 1.4 dB at 94 GHz have been measured, and multistage amplifiers with 1.7-dB noise figure at 62 GHz and 3.3 dB at 92 GHz are reported. Pseudomorphic HEMTs that exhibit the best power performance of any millimeter-wave transistor have been developed, with record output powers of 658, 125, and 57 mW at 35, 60, and 94 GHz, respectively, and power-added efficiency as high as 41% at 60 GHz. A 44-GHz pseudomorphic HEMT power amplifier has generated 0.25-W output power with 27% power-added efficiency and 14-dB power gain. Finally, the reliability of the various HEMT types is discussed. >

State-of-the-art high-electron-mobility-transistor (HEMT) devices have been fabricated on InAlAs/InGaAs/InP. Devices with 30- mu m and 50- mu m gate widths and 0.15- mu m gate length were fabricated using an all-electron-beam lithography process. After mesa formation, ohmic contacts were formed using a standard NiAuGe metallization. The contacts were annealed using a rapid thermal annealer. Typical ohmic contact resistance was approximately 0.13 Omega -mm. This is the same as the typical contact for the GaAs-based pseudomorphic HEMT result. Gates were defined using a trilayer resist scheme and recessed using a wet chemical etch to reach the desired channel current. A TiPtAu metallization forms the gate. The devices exhibited performance superior to most other low noise HEMT devices. It is found that the gate leakage current increases as recess depth increases. This current increase seems to degrade noise performance. >

Short-gate-length high-electron-mobility transistors (HEMTs) are reported that have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies; minimum noise figure of 1.2 dB at 32 GHz and 1.8 dB at 60 GHz from 0.25- mu m HEMTs. At Ka-band, a two-stage low-noise amplifier has demonstrated an average noise figure of 2 dB from 26.5 GHz to 37 GHz with a gain of 17 dB at 32 GHz. At V-band, a two-stage amplifier yielded a noise figure of 3.2 dB at 61 GHz with flat gain 12.7*0.5 dB from 59 GHz to 65 GHz. These devices are described and the potential for their future improvement is discussed. >

High-performance InAlAs/InGaAs planar-doped HEMTs (high-electron-mobility transistors) lattice-matched to InP have been fabricated with a 0.25- mu m T-gate. A maximum extrinsic transconductance g/sub m/ of 900 mS/mm, corresponding to an intrinsic g/sub m/ of 1640 mS/mm, was obtained at room temperature. RF measurements at 18 GHz yielded a minimum noise figure of 0.5 dB with an associated gain of 15.2 dB and a maximum stable gain of 20.9 dB. At 58 GHz, the devices exhibited a 1.2-dB minimum noise figure with an 8.5-dB associated gain. At 63 GHz, a maximum available gain of 15.4 dB was measured for a single-stage amplifier. This value, extrapolated to -6 dB/octave, yielded a maximum frequency of oscillation f/sub max/ of 380 GHz, which is the highest f/sub max/ ever reported for any transistor. A three-stage HEMT amplifier exhibited an average noise figure of 3.0 dB with a gain of 22.0+or-0.2 dB from 60-65 GHz. >

The development of InGaAs pseudomorphic high-electron mobility transistors (HEMTs) with state-of-the-art power performance at millimeter-wave frequencies is reported. Results given include maximum power-added efficiencies of 44% at 35 GHz and 36% at 44 GHz, output power of 100 mW with 22% efficiency and 3-dB gain at 60 GHz, and output power of 9 mW at 94 GHz. Preliminary reliability data are presented, and prospects for further improvement in performance-the realization of multifinger HEMTs capable of higher output power and reduction of gate length to 0.1 mu m-are discussed. >

A pseudomorphic HEMT (high electron mobility transistor) with record output power and high efficiency at 44 GHz has been developed. The 0.15 mu m gate-length, 900 mu m gate-width device generates 500 to 700 mW of output power with power-added efficiencies ranging from 22 to 30%. Moreover, the devices are producible: DC yields for these large gate-width HEMTs are 50-80% and uniformity of electrical characteristics is excellent. Reliability aspects of the device are discussed and the results of high-temperature DC life testing of pseudomorphic power HEMTs are reported. >

Double-heterojunction InGaAs pseudomorphic HEMTs (high electron mobility transistors) with a 0.25 mu m gate-length have been integrated into a three-stage power amplifier MMIC (monolithic microwave integrated circuit) designed for the 34-36 GHz band. This first pass design exhibited a peak small-signal gain of 30 dB, a minimum output power of 200 mW with 20 dB associated gain, a power-added efficiency of greater than 18%, and a return loss of greater than 14 dB over the entire band. This performance was measured with the MMIC operating from a single 6 V DC supply. >

We have demonstrated the first CBE growth of InP using bisphosphinoethane as a group V source. Mirrorlike surface morphology and excellent reflection high‐energy electron diffraction patterns were observed. Room temperature and 77 K Hall mobilities for a 2.0 μm thick InP epitaxial layer were 4200 and 22 000 cm2/V s, with carrier densities of 5.7×1015 and 4.0×1015 cm−3, respectively. Although a high n‐type impurity concentration is observed at the epitaxial layer‐substrate interface, the epitaxial layer background impurity concentration is low enough for device fabrication. The full width at half maximum linewidth of the dominant donor bound exciton is 0.84 meV.

The reverse dynamic current-voltage (I-V) characteristics of a high performance MBE grown AlGaAs/GaAs based heterostructure optothyristor have been studied for high power pulsed switching applications. Switched current and dissipated energy per switching as a function of the blocking voltage are presented. Possible reverse switching mechanisms are also discussed in terms of the novel device structure. >

A high-performance MBE-grown AlGaAs/GaAs-based heterostructure optothyristor has been fabricated and characterized for high-power pulsed switching applications. An LEC undoped semi-insulating GaAs of 650 mu m in thickness was used as the voltage blocking layer and low-temperature GaAs grown at 200 degrees C was used to passivate the surface and to reduce the surface leakage current. The dynamic current-voltage characteristics have been measured up to 115 A and 1974 V, which corresponds to a field intensity of more than 30 kV/cm. The dissipated energy per switching as a function of device voltage has also been determined to be in the range of 2 mJ or lower. >

State‐of‐the‐art quality Al0.3Ga0.7As was achieved on both (111)B and (100) GaAs by molecular beam epitaxy. Low‐temperature photoluminescence linewidths of 2.9 and 2.4 meV were obtained for (111)B and (100) Al0.3Ga0.7As, grown at 650 and 700 °C, respectively, with nearly equivalent integrated luminescence intensity. This is the narrowest linewidth ever reported for (111) AlGaAs. The low growth temperature and high material quality of (111)B Al0.3Ga0.7As is expected to be an important factor to the future development of both electronic and optical heterostructure devices.

We report the successful growth of high quality molecular beam epitaxy (MBE) GaAs, AlGaAs, AlGaAs/GaAs modulation doped heterostructures and a GaAs/InGaAs/GaAs quantum well on GaAs (111)B substrates. Modulation doped heterostructures show a 77 K mobility of 145 500 cm2/V s with a sheet density of 5.0×1011 cm−2. Photoluminescence of (111)B GaAs indicates a lower carbon incorporation than achieved on (100) substrates. The low growth temperature and high material quality obtainable in (111)B growth will provide advantages for laser diodes and heterostructure field effect transistors.

Experimental data are presented on equivalent gate noise voltage from 1 to 10/sup 5/ Hz obtained from lattice-matched and strained InGaAs quantum-well modulation-doped field effect transistors (MODFETs). In both types of devices excess generation-recombination (g-r) noise is observed at or below 100 Hz above an 'apparent' background 1/f noise with spectral intensity ranging from 0.5*10/sup -17/ to 2*10/sup -17/ V/sup 2/-Hz/sup -1/-cm/sup 2/ at 1 Hz. These results are comparable to those reported by S.M.J. Liu et al. (1986) for the pseudomorphic MODFETs. >

It is reported that 0.1- mu m T-gate InAlAs-InGaAs-InP HEMTs have exhibited state-of-the-art noise and gain performance well up to 100 GHz. Minimum noise figures of 0.8 and 1.2 dB with gains of 8.9 and 7.2 dB have been measured at 60 and 94 GHz, respectively. A high-performance W-band three-stage amplifier has been built using these devices with noise figures between 3.2-3.5 dB and a gain of 17.5+or-0.4 dB from 91 to 96 GHz. A 6-dB improvement in the 1-dB compression characteristic of the amplifier had been achieved with a GaAs pseudomorphic HEMT in the third stage. >

We have developed a new concept of narrow (50-80 /spl Aring/) channel MODFETs. It is shown theoretically and experimentally that only the ground energy level is populated in the narrow-channel device. A new technique to measure mobility at the highest energies of the two-dimensional electron gas (2-DEG) was introduced. With the help of this technique it is shown that, in wide wells, electrons in the excited energy levels have low mobility and consequently degrade device performance. It is shown theoretically and experimentally that the narrow-channel device has a higher electron sheet density and mobility and consequently better performance than a conventional wide-channel MODFET. Excellent quality Ga/sub x/In/sub 1-x/P/In/sub y/Ga/sub 1-y/As/GaAs MODFETs with a pseudomorphic barrier and a pseudomorphic channel were grown by MBE and OMVPE. Higher than 3.4/spl middot/10/sup 12/ cm/sup -2/ electron sheet densities for single-side-doped MODFETs on GaAs substrate were measured. One-tenth micron gate length MODFETs achieved f/sub T/'s over 100 GHz and f/sub max/'s over 180 GHz. These results are comparable to the previously reported results for GaInP MODPET with graded barriers, however the device structure is much simpler.

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterostructure have been grown on InP by molecular beam epitaxy. At room temperature, typical sheet charge densities of 2.1–3.0×1012 cm−2 and Hall electron mobilities over 10000 cm2 /V-s are obtained. An electron mobility as high as 13000 cm2 /V-s is achieved with a pseudomorphic Iny Ga1−y As channel and a y value of 0.70.HEMTs with a T- or Γ-shaped gate and with gate lengths ranging from 0.1–0.25 urn have been fabricated. A record low noise figure of 0.7 dB with an associated gain of 8.6 dB at 62 GHz has been achieved with 0.1 μm Γ-gate devices, while T-gate devices exhibit a minimum noise figure of 1.2 dB with 7.2 dB associated gain at 94 GHz. Separately, a record fmax value of 455 GHz was determined by extrapolating at -6 dB/octave from the measured gain of 13.6 dB at 95 GHz.Power HEMTs using a double heterojunction structure exhibit a record peak power-added efficiency (P.A.E.) of 49% with 8.6 dB power gain and 0.30 W/mm power density measured at 60 GHz. When biased and tuned for maximum output power, our best 60 GHz output power density to date is 0.52 W/mm with 33% P.A.E. and 5.9 dB power gain using a single heterojunction HEMT scheme with pseudomorphic channel. A similar device also yields peak P.A.E. of 26% with 0.20 W/mm power density and 4.9 dB gain at 94 GHz. These results represent the highest P.A.E.S and power gains ever reported for any transistor at these frequencies.

MBE GaAs grown at low temperature (300°C) is evaluated for its suitability as a buffer layer for microwave power FETs. Hall effect and capacitance-voltage (C-V) measurements show that low temperature (LT) buffers may have strong deleterious effects on the electronic quality of FET active layers unless they are heat-treated in-situ at 600'C and topped with a thin (∼0. lμm) 600°C GaAs buffer prior to growth of the FET active layer. The voltage isolation properties of the LT buffers are found to be thermally stable to rapid thermal anneals up to 870°C for 10 seconds.Transmission electron microscopy (TEM) cross-sections were examined on FET layers with LT buffer layers which ranged in thickness from 0.1μm to 1.0μm. The TEM reveals a high density (∼1017 cm−3) of small (

Extremely low-noise O.15jim gate-length V- and W-band InGaAs I InAlAs I InP lattice-matched and pseudomorphic HEMTs have been successfully fabricated. A maximum extrinsic transconductance of 1,500mS/mm and a gate breakdown voltage of more than 1OV have been obtained for the devices. Minimum noise figures of 0.3, 0.9 and and 1.4dB have been measured for the devices at 18, 60 and 94GHz, respectively. We have also measured a maximum available gain of 13.6dB at 95GHz, corresponding to a maximum frequency of oscillation, m' of 455GHz (-6dB/octave extrapolation) with the device. Based on these high performance O.l5Rm devices, a 3-stage hybrid amplifier with a minimum noise figure of 3.3dB and gain of 17.3±0.5dB from 88 to 96GHz has been built. We have also successfully demonstrated for the first time a two-stage InP-based HEMT monolithic microwave integrated circuit (MMIC) with 3.0dB noise figure and 21.0dB gain at 58GHz. These are the best device and amplifier results ever reported. The results are far superior to those obtained from the GaAs-based MESFET and HEMT technology, and clearly demonstrate the potential of the InP-based HEMT technology for very low-noise applications well into the millimeter-wave regime.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

AlGaAs/InGaAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700mS/mm. At 18GHz, a minimum noise figure of 0.55dB with 15.0dB associated gain was measured. At 94GHz, a minimum noise figure as low as 2.4dB with 5.4dB associated gain was also obtained. This is the best noise performance ever reported for GaAs-based HEMTs.

The development of HEMTs based on the InAlAs/InGaAs/InP materials system for high-frequency analog applications is reported. Devices with 0.15- mu m gatelengths have demonstrated extrinsic transconductance of 1500 mS/mm and extrapolated maximum frequency of oscillation f/sub max/ greater than 450 GHz. The noise figure is the lowest of any room-temperature receiver technology over the 5 to 100 GHz frequency range. Prospects for power amplification are excellent: power-added efficiency of 41% has already been demonstrated at 60 GHz. The integration of these devices into monolithic microwave integrated circuits (MMICs) is discussed. >

The authors report 0.15- mu m gate length GaAs-based and InP-based InGaAs channel high-electron-mobility transistors (HEMTs) that have exhibited state-of-the-art noise and gain performance well up to 100 GHz. 94-GHz noise figures of 2.4 and 1.4 dB with gains of 5.4 and 6.5 dB have been measured from GaAs- and InP-based HEMTs, respectively. High-performance W-band multistage amplifiers have been built using these devices. A two-stage GaAs-based amplifier exhibits a noise figure of 4.2 dB with a gain of 9.7 dB at 93 GHz, and a three-stage amplifier yields a 4.5-dB noise figure with 14.8-dB gain at 94 GHz. The best two-stage amplifier built with InP-based HEMTs exhibits a minimum noise figure of 3.2 dB with a gain of 11.5+or-0.4 dB from 88 to 96 GHz. A noise figure as low as 3.3 dB with gain of 17.3+or-0.5 dB from 88 to 96 GHz has also been demonstrated from a three-stage amplifier. The characteristics and performance of both devices are presented. >

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.

We report the successful growth of high‐quality molecular‐beam epitaxy (MBE) GaAs, AlGaAs, AlGaAs/GaAs modulation‐doped heterostructures, GaAs/InGaAs/GaAs quantum well, and AlGaAs/InGaAs multiple quantum wells (NQW) on GaAs (111)B substrates. Modulation‐doped heterostructures show a 77‐K mobility of 145 500 cm2/V s with a sheet density of 5.0×1011 cm−2. Photoluminescence of (111)B GaAs indicates a lower carbon incorporation than achieved on (100) substrates. The high material quality obtainable at low growth temperatures for (111)B growth will be advantageous for laser diode and heterostructure field‐effect transistor applications. AlGaAs/InGaAs MQW on (111)B are comparable in the photoluminescence linewidths to those on (100) GaAs.

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterojunction grown lattice matched to InP were fabricated with 0.15 μm T-shaped gates. The use of an undoped InGaAs cap layer in the epitaxial structure leads to excellent gate characteristics and very high transistor gain. At 95 GHz, a maximum available gain of 13.6 dB was measured. A maximum frequency of oscillation fmax of 455 GHz was obtained by extrapolating from 95 GHz at –6 dB/octave. This is the best reported gain performance for any transistor.

A 0.25μm gate length, 1600μm gate width, doubleheterojunction pseudomorphic HEMT with moderate output power and record power gain and efficiency is reported. At 15 GHz, output power is 575 mW with 12dB gain and 50% power-added efficiency.

Quarter-micron-gate-length high-electron-mobility transistors (HEMTs) have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies, with minimum noise figures of 1.2 dB and 32 GHz and 1.8 dB at 60 GHz. At Ka-band, two-stage and three-stage HEMT low-noise amplifiers have demonstrated noise figures of 1.7 and 1.9 dB, respectively, with associated gains of 17.0 and 24.0 dB at 32 GHz. At V-band, two stage and three-stage HEMT amplifiers yielded noise figures of 3.2 and 3.6 dB, respectively, with associated gains of 12.7 and 20.0 dB and 60 GHz. The 1-dB-gain compression point of all the amplifiers is greater than +6 dBm. The results clearly show the potential of short-gate-length HEMTs for high-performance millimeter-wave receiver application. >

The cryogenic noise temperature performances of a two-stage and a three-stage 32-GHz HEMT (high-electron-mobility transistor) amplifier were evaluated. The amplifiers utilize quarter-micrometer conventional AlGaAs/GaAs HEMT devices, hybrid matching input and output microstrip circuits, and a cryogenically stable DC biasing network. The noise temperature measurements were performed in the frequency range of 31 to 33 GHz over a physical temperature range of 300 to 12 K. Across the measurement band, the amplifiers displayed a broadband response, and the noise temperature was observed to decrease by a factor of ten in cooling from 300 to 15 K. The lowest noise temperature measured for the two-stage amplifier at 32 GHz was 35 K with an associated gain of 16.5 dB, while for the three-stage amplifier it was 39 K with an associated gain of 26 dB. It was further observed that both amplifiers were insensitive to light. >

Quarter-micrometer gate-length high-electron-mobility transistors (HEMTs) for cryogenic low-noise application with very low light sensitivity have been developed. At room temperature, these exhibit a noise figure of 0.4 dB with associated gain of 15 dB at 8 GHz. At a temperature of 12.5 K the minimum noise temperature of 5.3+or-1.5 K has been measured at 8.5 GHz, which is the best noise performance observed to date for any microwave transistors. The results clearly demonstrate the potential for low-temperature low-noise applications. >

Analytical modeling of these very-short-channel HEMTs (high-electron-mobility transistors) using the charge-control model is given. The calculations performed using this model indicate a very high electron velocity in the device channel (3.2+or-0.2*10/sup 7/ cm/s) and clearly demonstrate the advantages of the planar-doped devices as compared to the conventional uniformly doped HEMTs. Devices with different air-bridged geometries have been fabricated to study the effect of the gate resistance on the sub-0.1- mu m HEMT performance. With reduced gate resistance in the air-bridge-drain device, noise figures as low as 0.7 and 1.9 dB were measured at 18 and 60 GHz, respectively. Maximum available gains as high as 13.0 dB at 60 GHz and 9.2 dB at 92 GHz, corresponding to an f/sub max/ of 270 GHz, have also been measured in the device. Using the planar-doped pseudomorphic structure with a high gate aspect-ratio design, a noise figure of less than 2.0 dB at 94 GHz is projected based on expected further reduction in the parasitic gate and source resistances. >

AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (HEMT's) with a gate length of 0.1 µm have been successfully fabricated. The HEMT's exhibit a maximum transconductance of 540 mS/mm with excellent pinch-off characteristics. A maximum stable gain (MSG) as high as 18.2 dB was measured at 18 GHz. At 60 GHz the device has demonstrated a minimum noise figure of 2.4 dB with an associated gain of ∼6 dB. These are the best gain and noise results reported to date for HEMT's.

Room-temperature noise performance of high-electron-mobility transistors (HEMTs) has been studied by correlating the microwave/millimeter-wave noise figure with lower frequency model parameters. By comparing devices fabricated from various molecular-beam epitaxially grown wafers, it is found that devices with high transconductance at low drain current generally exhibit superior noise performance. In particular, an optimal noise figure of 1.8 dB has been obtained at 60 GHz with 6.4-dB associated gain for devices from the best wafer. The low thermal noise coefficient ( theta >

0.15- mu m-gate-length double-heterojunction pseudomorphic high electron mobility transistors (HEMTs) for which excellent millimeter-wave power and noise performance were achieved simultaneously are reported. The 50- mu m-wide HEMTs yielded record maximum power-added efficiencies of 51, 41, and 23% at 35, 60, and 94 GHz, respectively. Maximum output powers of 139 mW at 60 GHz and 57 mW at 94 GHz were also measured for 150- mu m-gate-width devices. Finally, minimum noise figures as low as 0.55 and 1.8 dB were measured at 18 and 60 GHz respectively. This is the best power and noise performance yet reported for passivated transistors at millimeter-wave frequencies. >

The 94-GHz power performance of a 0.25*75- mu m doped-channel pseudomorphic heterostructure FET (HFET) is reported. A maximum output power of 32 mW, corresponding to a power density of 0.43 W/mm, was obtained with 15% power-added efficiency and 3.0 dB gain. >

The thin strained superlattice (TSSL) concept is introduced as a means for extending the practical range of application for pseudomorphic Inx Ga1−x As on GaAs. Growth and characterization results are presented for pseudomorphic high electron mobility transistor structures with GaAs‐In0.3 Ga0.7 As TSSL active layers grown by molecular beam epitaxy. The TSSLs are composed of three periods of GaAs(15 A)‐ In0.3 Ga0.7 As(h2 ), where h2 ranges from 30 to 52 A. Modulation doping of the TSSLs is provided by atomic planar‐doped Al0.3 Ga0.7 As overlayers with 45 A undoped spacers. 77 K Hall effect and transmission electron microscopy reveal that relatively thick TSSLs can be grown with high electronic and structural quality, comparable to much thinner In0.3 Ga0.7 As single quantum wells. Results are compared with a model for critical layer thickness and discussed in light of in situ reflection high‐energy electron diffraction measurements.