The design and fabrication of a class of 50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors (HEMTs) with potential for ultra-high-frequency and ultra-low-noise applications are reported. These devices exhibit an extrinsic transconductance of 1740 mS/mm and an extrinsic current-gain cutoff frequency of 340 GHz at room temperature. The small-signal characteristics of a pseudomorphic and a lattice-matched AlInAs/GaInAs HEMT with similar gate length (50 nm) and gate-to-channel separation (17.5 nm) are compared. The former demonstrates a 16% higher transconductance and a 15% higher current-gain cutoff frequency, but exhibits a 38% poorer output conductance. An analysis of the high-field transport properties of ultra-short gate-length AlInAs/GaInAs HEMTs shows that a reduction of gate length from 150 to 50 nm neither enhances nor reduces their average velocity. In contrast, the addition of indium from 53% to 80% improves this parameter by 19%. >

50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors

A tutorial review on the modulation-doped field-effect transistor (MODFET) and its application to ultra-low-noise, medium-power, and ultra-wide-band traveling-wave amplifiers as well as ultra-high-speed digital logic circuits is presented. It is believed that with further advances in material growth and device scaling significant improvements in cutoff frequencies, switching speed, noise, and power will be achieved in the near future. >

Ultra-high speed modulation-doped field-effect transistors: a tutorial review

We report here 305 GHz f/sub T/, 340 GHz f/sub max/, and 1550 mS/mm extrinsic g/sub m/ from a 0.10 /spl mu/m In/sub x/Ga/sub 1-x/As/In/sub 0.62/Al/sub 0.48/As/InP HEMT with x graded from 0.60 to 0.80. This device has the highest f/sub T/ yet reported for a 0.10 /spl mu/m gate length and the highest combination of f/sub T/ and f/sub max/ reported for any three-terminal device. This performance is achieved by using a graded-channel design which simultaneously increases the effective indium composition of the channel while optimizing channel thickness. >

0.10 /spl mu/m graded InGaAs channel InP HEMT with 305 GHz f/sub T/ and 340 GHz f/sub max/

As a first approach to the study of strained pseudomorphic materials, we have used a Monte Carlo method to calculate the effect of strain on electron transport properties of bulk InGaAs. Strain‐induced velocity reduction is found to be much more pronounced for InGaAs grown on GaAs substrate than for InGaAs grown on InP substrate.

Electron transport properties of strained InxGa1−xAs

The design and fabrication using low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) of a HEMT on InP substrate that only uses InP and In/sub x/Ga/sub 1-x/As as layer materials are reported. Lattice-matched (x=0.53) and strained (x=0.68) channels and a double-heterojunction design were used in this investigation. The DC performance of the 0.8- mu m devices at 300 and 77 K was excellent for both cases. Improvements of 9 and 22% in g/sub mext/ with the strain were measured at the same temperatures, in accordance with theoretical predictions. The approach described may serve as a very useful alternative, especially in MOVPE growth, to InAlAs containing structures because it eliminates many of the troublesome effects such as kinks, deep levels, interface states, high output conductances, and gate leakage, which are to a large extent attributed to impurity-Al interactions. The use of lattice-mismatched InGaAs as channel layer increases the conduction band offset to InP, the DH structure improves both confinement and current, and the p-InP barrier layer results in sufficiently high quasi-Schottky barriers. >

Double-heterojunction lattice-matched and pseudomorphic InGaAs HEMT with delta -doped InP supply layers and p-InP barrier enhancement layer grown by LP-MOVPE

We have grown pseudomorphic InxGa1−xAs/In0.52Al0.48As modulation‐doped heterostructures by molecular‐beam epitaxy under carefully controlled growth conditions. Mobilities as high as 13 900, 74 000, and 134 000 cm2/V s are measured at 300, 77, and 4.2 K in a heterostructure with x=0.65. Shubnikov–de Haas measurements indicate that the change in the effective mass with increasing In is not significant and is not responsible for the enhancement in mobilities. We believe that the improvement results from reduced alloy scattering, reduced intersubband scattering, and reduced impurity scattering, all of which result from a higher conduction‐band offset and increased carrier confinement in the two‐dimensional electron gas. The high‐field electron velocities have been measured in these samples using pulsed current‐voltage and pulsed Hall measurements. A monotonic increase in velocities is observed both at 300 and 77 K with an increase of In content in the channel. Velocities of 1.55×107 and 1.87×107 cm/s are meas...

W.‐P. Hong

Papers

Low‐ and high‐field transport properties of pseudomorphic InxGa1−xAs/In0.52Al0.48As (0.53≤x≤0.65) modulation‐doped heterostructures