M.J. Delaney

Microwave performance of AlInAs-GaInAs HEMTs with 0.2- and 0.1- mu m gate length

The millimeter-wave performance is reported for Al/sub 0.48/In/sub 0.52/As-Ga/sub 0.47/In/sub 0.53/As high-electron-mobility transistors (HEMTs) with 0.2- mu m and 0.1- mu m-long gates on material grown by molecular-beam epitaxy on semi-insulating InP substrates. Devices of 50- mu m width exhibited extrinsic transconductances of 800 and 1080 mS/mm, respectively. External f/sub T/ (maximum frequency of oscillation) of 120 and 135 GHz, respectively, were measured. A maximum f/sub T/ of 170 GHz was obtained from a 0.1*200- mu m/sup 2/ device. A minimum noise figure of 0.8 dB and associated gain of 8.7 dB were obtained from a single-stage amplifier at frequencies near 63 GHz.<<ETX>>

High-performance submicrometer AlInAs-GaInAs HEMT's

The performance of long (1.3- mu m) and short (0.3- mu m) gate-length Al/sub 0.48/In/sub 0.52/ As-Ga/sub 0.47/In/sub 0.53/ high-electron-mobility transistors (HEMTs) is reported. Transconductances of 465 and 650 mS/mm, respectively, were achieved. The 0.3- mu m-long gate-length device exhibited an f/sub t/>80 GHz. These results are attributed to the excellent electronic properties of the AlInAs-GaInAs modulation-doped system.<<ETX>>

AlInAs-GaInAs HEMTs utilizing low-temperature AlInAs buffers grown by MBE

Low-temperature AlInAs buffer layers incorporated in AlInAs-GaInAs HEMT epitaxial layers grown by MBE are discussed. A growth temperature of 150 degrees C followed by a short anneal is shown to eliminate kinks in the device I-V characteristic and sidegating and to reduce the output conductance dramatically.<<ETX>>

GaN double heterojunction field effect transistor for microwave and millimeterwave power applications

We report development of a novel AlGaN/GaN/AlGaN double heterojunction field effect tansistor (DHFET) with improved device performance over the conventional single heterojunction GaN FET (SHFET). The GaN DHFETs with low Al content Al/sub 0.04/Ga/sub 0.96/N buffer layer exhibit three orders of magnitude lower subthreshold drain leakage current and almost three orders of magnitude higher buffer isolation than corresponding SHFET devices (600 M/spl Omega//sq. vs. 1 M/spl Omega//sq.). In GaN DHFETs with 0.15 /spl mu/m conventional T-gates we observed 30% improvement in saturated power density and 10% improvement in PAE at 10 GHz over a corresponding SHFET device.

AlInAs-GaInAs HEMT for microwave and millimeter-wave applications

The status of lattice-matched high-electron-mobility transistors (HEMTs) and pseudomorphic AlInAs-GaInAs grown on In substrates is reviewed. The best lattice-matched devices with 0.1- mu m gate length had a transconductance g/sub m/=1080 mS/mm and a unity current gain cutoff frequency f/sub T/=178 GHz, whereas similar pseudomorphic HEMTs had g/sub m/=1160 mS/mm and f/sub T/=210 GHz. Single-stage V-band amplifiers demonstrated 1.3- and 1.5-dB noise figures and 9.5- and 8.0-dB associated gains for the lattice-matched and pseudomorphic HEMTs, respectively. The best performance achieved was a minimum noise figure of F/sub min/=0.8 dB with a small-signal gain of G/sub a/=8.7 dB. >

The impact of epitaxial layer design and quality on GaInAs/AlInAs high‐electron‐mobility transistor performance

Ga0.47In0.53As–Al0.48In0.52As high‐electron mobility transistors (HEMT’s) exhibit high transconductance and gain because of the high conductivities achievable in the structures. The effect of epitaxial layer design (spacer thickness and active channel thickness) on conductivity is examined. Device characteristics are examined as a function of active channel thickness. Reduced output conductance is observed for a 200 A channel, but with a reduced transconductance.

The effect of inhibited growth kinetics on GaInAs and AlInAs alloy and interface quality

Ga0.47In0.53As and Al0.48In0.52As alloys, lattice matched to InP substrates, are typically grown under conditions (low substrate temperature and high V/III flux ratios) which limit cation surface mobilities. For the (Al,Ga)As system, the growth of material with low‐defect density and good microscopic surface morphology is dependent on highly mobile cations which can reach kink sites on the growing surface. In the (Al,In,Ga)As system, other factors such as the miscibility gap in the AlInAs phase diagram and the volatility of InAs component dominate the growth condition requirements. In order to determine the role kinetic limitations play in reducing the quality of GaInAs and AlInAs under ‘‘normal’’ molecular beam epitaxy growth conditions, epitaxial layers were grown at extremely low substrate temperatures and high V/III ratios to examine the sensitivity of materials properties to these growth conditions.

The effect of InP substrate misorientation on GaInAs‐AlInAs interface and alloy quality

The quality of GaInAs‐AlInAs epitaxial layers is found to be critically dependent on the degree of (100)‐InP substrate misorientation. The alloy quality of both materials is improved when the substrate is misoriented 4° off the (100). The heterojunction interface quality as determined by the full width at half‐maximum of quantum‐well photoluminescence is also improved when a substrate misoriented by 4° is used. A degradation of both alloy and interface quality as compared to material on (100) InP is observed when the misorientation is 2°. These effects are also observed for strained quantum‐well structures.

V-band high-efficiency high-power AlInAs/GaInAs/InP HEMT's

The authors report on the state-of-the-art power performance of InP-based HEMTs (high electron mobility transistors) at 59 GHz. Using a 448- mu m-wide HEMT with a gate length of 0.15 mu m, an output power of 155 mW with a 4.9-dB gain and a power-added efficiency of 30.1% were obtained. By power-combining two of these HEMTs, an output power of 288 mW with 3.6-dB gain and a power-added efficiency of 20.4% were achieved. This is the highest output power reported with such a high efficiency for InP-based HEMTs, and is comparable to the best results reported for AlGaAs/InGaAs on GaAs pseudomorphic HEMTs at this frequency. >

Ka-band MMIC power amplifier in GaN HFET technology

We report the development of Ka-band GaN MMIC power amplifiers in CPW and microstrip topologies. This is, to the best of our knowledge, the first demonstration of millimeter wave MMICs in GaN technology. The single stage CPW MMIC utilizes four 2/spl times/100 /spl mu/m wide GaN HFETs whilst four 4/spl times/60 /spl mu/m wide HFETs with individual through substrate source vias were used for the microstrip MMICs. The CPW amplifier has a gain peak of 8 dB at 33 GHz with 4 GHz bandwidth while the microstrip amplifier has a peak gain of 9 dB at 27 GHz and gain higher than 8 dB over the 2.45 GHz to 33 GHz frequency range. The saturated CW output power of the amplifiers measured into a 50 /spl Omega/ system at 33 GHz was, respectively, 1.6 W for the microstrip MMIC. The corresponding power density of 2.3 W per mm of gate periphery for the microstrip MMIC is by a factor of 4 higher than that of a typical GaAs pHEMT MMIC at this frequency. Microstrip MMIC performance was further improved through external output impedance matching, resulting in power levels of up to 2.8 W (27% associated PAE) and peak PAEs of up to 36.2% (1.2 W associated power).