AlGaAsSb/InGaAs/AlGaAsSb metamorphic HEMTs

Deep quantum well In_0.8Ga_0.2As/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 cm²/V-sec at 300 K for carrier concentrations of 2.4×10¹² cm^-2. Extrinsic DC transconductance of 820 mS/mm was obtained for an MHEMT with a 0.15 μm×64 μm gate. Typical extrinsic unity current gain cutoff, f_t, was 173 GHz with maximum frequency of oscillation, f_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.