D X centers in AlGaAs p-n heterojunctions and heterojunction bipolar transistors

D X centers are found to cause the capacitance of an AlGaAs/GaAs p-n heterojunction at 77 K to behave like that of a p-i-n diode. Exposure to light causes the capacitance to behave like a normal p-n junction. It is argued that the presence of DX centers has only a small effect on the switching properties heterojunction bipolar transistors.