AlSb/InAs HEMT's for low-voltage, high-speed applications

The design, fabrication, and characterization of 0.1 mu m AlSb/InAs HEMT's are reported. These devices have an In0.4Al0.6As/AlSb composite barrier above the InAs channel and a p(+) GaSb Layer within the AlSb buffer layer, The HEMT's exhibit a transconductance of 600 mS/mm and an f(T) of 120 GHz at V-DS = 0.6 V, An intrinsic f(T) of 160 GHz is obtained after the gate bonding pad capacitance is removed from an equivalent circuit. The present HEMT's have a noise figure of 1 dB with 14 dB associated gain at 4 GHz and V-DS = 0.4 V, Noise equivalent circuit simulation indicates that this noise figure is primarily limited by gate leakage current and that a noise figure of 0.3 dB at 4 GHz is achievable with expected technological improvements. HEMT's with a 0.5 mu m gate length on the same wafer exhibit a transconductance of 1 S/mm and an intrinsic f(T)L(g) product of 50 GHz-mu m.