Scanning capacitance microscopy of AlGaN/GaN heterostructure field-effect transistor epitaxial layer structures

Scanning capacitance microscopy is used to characterize local electronic pr operties in an AlxGa1-xN/GaN heterostructure field-effect transistor epitax ial layer structure. Lateral inhomogeneity in electronic properties is clea rly observed, at length scales ranging from similar to 0.1 to > 2 mu m, in images obtained at fixed bias voltages. Acquisition of a series of images o ver a wide range of bias voltages allows local electronic structure to be p robed with nanoscale spatial resolution both laterally and in depth. Combin ed with theoretical analysis of charge and potential distributions in the e pitaxial layer structure under applied bias, these studies suggest that the dominant factor contributing to the observed variations in electronic stru cture is local lateral variations in AlxGa1-xN layer thickness. (C) 1999 Am erican Institute of Physics. [S0003-6951(99)01441-2].