AlGaAsSb/InGaAs/AlGaAsSb metamorphic HEMTs

Deep quantum well In/sub 0.8/Ga/sub 0.2/As/AlGaAsSb MHEMTs on GaAs are described. The step-graded AlGaAsSb strain-relief buffer layer provided a high-quality surface for growth of the MHEMT layers. AlGaAsSb barrier layers offer flexibility in choosing the channel composition and the barrier height. Typical Hall mobilities were 11,000 cm/sup 2//V-sec at 300 K for carrier concentrations of 2.4/spl times/10/sup 12/ cm/sup -2/. Extrinsic DC transconductance of 820 mS/mm was obtained for an MHEMT with a 0.15 /spl mu/m/spl times/64 /spl mu/m gate. Typical extrinsic unity current gain cutoff, f/sub t/, was 173 GHz with maximum frequency of oscillation, f/sub max/, of 474 GHz. Aside from layer growth, the MHEMTs were fabricated using only small changes from conventional GaAs PHEMT processing. This technology promises affordable production costs for high performance millimeter-wave low noise amplifiers.