Optical properties of Mg-implanted GaN grown on free-standing substrates

Abstract In this work, unintentionally doped GaN thin films were successfully grown on (0001) c -, (11–20) a - and (10–10) m -plane GaN free-standing substrates using metal–organic chemical vapor deposition. Subsequently, Mg was introduced into the GaN thin films through ion implantation (I/I) to prepare Mg-doped GaN (GaN:Mg). Compared with the c -plane substrate, non-polar a - and m -plane substrates were found to effectively enhance the concentration of Mg Ga acceptors while reducing the concentration of nitrogen vacancy-related clusters in I/I GaN:Mg. The origins of the ultraviolet luminescence peak, green luminescence band and blue luminescence band were analyzed by photoluminescence (PL) spectra. Two acceptor energy levels of Mg in I/I GaN:Mg were calibrated by measuring low-temperature PL spectra in the range of 5 K to 50 K.