HIGH-TEMPERATURE PERFORMANCE AND OPERATION OF HFETS

The high temperature performance of Al0.75Ga0.25As/In0.25Ga0.75As/GaAs Complementary Heterojunction FET's (CHFET's) is reported between 25 a nd 500 degrees C, Both experimental and modeled devices have shown acc eptable digital characteristics to 400 degrees C, Digital logic circui ts have also been shown to operate at temperatures of over 400 degrees C, This strongly suggests that GaAs based devices are capable of sati sfying high temperature electronics requirements in the 125-400 degree s C range. Two dimensional physically based modeling has been used to understand the high temperature operation of the HFET's, This work has shown that the devices suffer from gate limited drain leakage current s at elevated ambient temperatures, This off-state leakage current is higher than anticipated, Simulation has shown that, although forward g ate leakage currents are reduced with the heterostructure device desig n, the reverse current is not.