Surface photovoltage spectroscopy of a GaAs/AlGaAs heterojunction bipolar transistor

The electronic properties of a GaAs/AlGaAs heterojunction bipolar transistor (HBT) structure have been studied by surface photovoltage spectroscopy. The p-base band-gap narrowing has been determined and confirmed by numerical simulation. Based on the shape of the surface photovoltage spectrum, it is possible to monitor the doping level and evaluate the minority-carrier mobility. This work demonstrates the power of the technique as a precision tool for HBT quality control.