High temperature performance and operation of HFETs

The high temperature performance of Al/sub 0.75/Ga/sub 0.25/As/In/sub 0.25/Ga/sub 0.75/As/GaAs Complementary Heterojunction FETs (CHFETs) is reported between 25 and 500/spl deg/C. Both experimental and modeled devices have shown acceptable digital characteristics to 400/spl deg/C. Digital logic circuits have also been shown to operate at temperatures of over 400/spl deg/C. This strongly suggests that GaAs based devices are capable of satisfying high temperature electronics requirements in the 125-400/spl deg/C range. Two dimensional physically based modeling has been used to understand the high temperature operation of the HFETs. This work has shown that the devices suffer from gate limited drain leakage currents at elevated ambient temperatures. This off-state leakage current is higher than anticipated. Simulation has shown that, although forward gate leakage currents are reduced with the heterostructure device design, the reverse current is not.