INXAL1-ZAS IN1-YAS LATTICE-CONSTANT ENGINEERED HEMTS ON GAAS/

We investigated the device performance of InaAl1-xAs/In1-yGa1-yAs latt ice constant engineered (LCE) HEMTs grown on a GaAs substrate utilizin g a low MBE growth temperature graded InzAl1-zAs buffer layer to accom modate the lattice mismatch between the GaAs substrate and the device heterostructure. Three InzAl1-zAs/InyGa1-yAs LCE HEMTs were fabricated with compositions of y,z = 0.30, 0.40, and 0.50. We present results f rom both d.c. and RF device characterization which shows that with inc reasing InAs composition (i.e. increasing y- and z-values), the Hall m obility, transconductance, maximum drain current of the LCE-HCEMT all increase. At the same time, however, increasing InAs content leads to a significant reduction in both the forward bias gate-to-drain turn-on voltage, and the reverse bias gate-to-drain breakdown voltage. The de pendence of the various device characteristics with InAs content all h ave significant implications for the optimization of LCE-HEMTs for mil limeterwave power device applications. (C) 1997 Elsevier Science Ltd.