Formation chemistry of high-density nanocraters on the surface of sapphire substrates with an in situ etching and growth mechanism of device-quality GaN films on the etched substrates

The growth of high-quality GaN films on sapphire substrates with high-density nanocraters was investigated. The nanocraters were formed on the surface of the substrates in situ a MOCVD reactor by GaN decomposition induced etching. The scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), Hall measurement and photoluminescence (PL) analysis were used for the characterization of the films. It was observed that the decomposition of GaN induced the decomposition of sapphire, which resulted in the formation of high density nanocraters on its surface.