Defect Studies of GaN under Large Hydrostatic Pressure

ABSTRACTGaN plays a key role in the exploration of the properties of group-Ill nitrides. As grown GaN often shows a high electron concentration, e.g. 1019 cm−3, of as yet unidentified origin. Applying large hydrostatic pressure we studied the behavior of these donors and a frequently observed strong luminescence band at 3.42 eV. We find a drop of the electron concentration to 3×1017 cm−3 at 27 GPa and derive a binding energy of 126 meV for the neutral singlet donor level at this pressure. Such a pressure behavior of a donor is consistent with the model of strongly localized defects. Within the framework of a bandstructure calculation we predict the neutral level of this donor at 0.40 ± 0.10 eV above the conduction band edge at ambient pressure.