Hot electron and DX center insensitivity of Al/sub 0.25/Ga/sub 0.75/As/GaAs HFET's designed for microwave power applications

We show in this work that, although designing Al/sub x/Ga/sub 1-x/As/GaAs HFET's for microwave power applications requires a large barrier layer bandgap (hence x>0.2), the presence of a large concentration of electrically active DX centers in the barrier layer does not hinder the device reliability. The existence of a remarkable quantity of DX centers in the Al/sub 0.25/Ga/sub 0.75/As barrier layer is for the first time revealed by means of room temperature electroluminescence, and their concentration is evaluated by measuring the threshold voltage shift induced by hot electron stress at cryogenic temperatures.