The influence of indium surfactant on the electrical properties of GaN epilayers grown by metal-organic chemical vapour deposition

Abstract

The electrical properties of GaN epilayers grown by metal-organic chemical vapour deposition adopting the indium-surfactant method have been investigated by means of Hall measurement, photoluminescence and monoenergetic positron annihilation spectroscopy. The background electron concentration in GaN exhibits a minimum of 5.21 × 1016 cm−3 for a trimethylindium (TMIn) flow of 20 µmol min−1. The decrease in electron concentration with increasing TMIn flow is likely related to an increase in the density of complex defects involving Ga vacancy (VGa), compensating the electrons. We speculate that the increase in electron concentration at high TMIn flow is caused by the formation of N vacancies (VN), acting as shallow donors. Competition between the two mechanisms may determine the variation of electron concentration with increasing TMIn flow. A downward trend in electron mobility with increasing TMIn flow is also observed, which likely results from an increase in concentration of complex defects involving VGa and VN.