High-temperature performance of GaAs-based HFET structure containing LT-AlGaAs and LT-GaAs

Using low-temperature grown layers a GaAs-based HFET structure was developed, which demonstrates for the first time high performance at high temperatures up to 540/spl deg/C, where the gate diode shunts through. The device was designed for operation in the hot electron regime using an LT-AlGaAs passivation layer. Thus, the open channel current density and gain bandwidth product are exceptionally stable (I/sub D500/spl deg/C//I/sub DR.T./=0.9; f/sup T200/spl deg/C/f/sub TR.T./=0.9). The f/sub max/ cutoff frequency is the most temperature sensitive parameter {(f/sub max//f/sub T/)/sub R.T./=3.9 and (f/sub max//f/sub T/)/sub 200/spl deg/C/=2.8} due to the thermal activation of the buffer layer leakage, which is kept extremely small using LT-GaAs.