DX-center-related features by capacitance measurements in AlGaAs

The role of quasistatic C-V measurements in investigating DX-center-related features in AlGaAs (x=0.25, 0.30, and 0.35) Schottky barriers has been reconsidered under different experimental conditions. The vanishing of the electron-capture rate by the DX center, at low temperature, is responsible for a frozen-step-like density profile of positively charged DX centers near the metal-semiconductor interface. This causes a knee-shaped 1/C2-vs-V plot and gives rise to an apparent built-in potential. The low-temperature freezing in of the free-electron density in the flatband region has been demonstrated through specific experiments of thermally stimulated capacitance and low-temperature C-V measurements performed on the sample cooled at different cooling rates