Charging effects in AlGaNÕGaN heterostructures probed using scanning capacitance microscopy

Charging effects in an AlxGa1 xN/GaN heterostructure field-effect transistor epitaxial layer structure have been studied using scanning capacitance microscopy. Voltages of 6 V applied between an AlxGa1 xN/GaN sample structure and a conducting proximal probe tip are found to create trapped charge in both doped and undoped heterostructures. Scanning capacitance measurements obtained over a wide range of bias voltages allow the charge distribution to be mapped both laterally and in depth with submicron to nanometer scale spatial resolution. Scanning capacitance imaging as a function of bias voltage performed in conjunction with numerical capacitance–voltage simulations suggests that positive charge can be trapped at the AlxGa1 xN surface and within the GaN layer and negative charge can be trapped at or near the AlxGa1 xN/GaN interface. © 2000 American Vacuum Society. S0734-211X 00 00604-1