Intrinsic compensation of silicon-doped AlGaN

The silicon doping characteristics of AlxGa1−xN were investigated over the x=0.2–0.5 composition range. A combination of Hall and capacitance–voltage measurements indicated a significant deepening of the Si level, as well as a systematic increase in carrier compensation with increasing compositions. Optical isothermal capacitance transient spectroscopy also revealed the presence of two midgap states with concentrations in the low 1017 cm−3 range. The two levels, which are thought to be responsible for the observed compensation, have been assigned to the third and second ionization states of the aluminum vacancy.