Vacancy-type defects in Mg-doped InN probed by means of positron annihilation

The introduction of vacancy-type defects into InN by Mg-doping was studied using a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured for Mg-doped InN (N-polar) grown on GaN/sapphire templates using plasma-assisted molecular beam epitaxy. The concentration of In-vacancy (VIn) related defects was high near the InN/GaN interface, and the defect-rich region expanded from the interface toward the surface with increasing Mg concentration [Mg]. Using electrolyte-based capacitance-voltage analysis, we determined that the conduction type of InN with low [Mg] (≤1×1018 cm−3) was still n-type. It became p-type with increasing [Mg] (3×1018–2×1019 cm−3), but turned into n-type again above 3×1019 cm−3. The point defects introduced at the conductivity transition from p-type and n-type were found to be complexes between In-vacancy (VIn) and N-vacancy clusters such as VIn(VN)3. Below [Mg]=4×1019 cm−3, an observed behavior of positron annihilation parameters was well explain...