Characterization of a-plane GaN films grown on r-plane sapphire substrate by electron microscopy

Abstract

Gallium nitride (GaN) is a semiconductor material which has recently attracted much attention for wide and direct band gap of 3.39 eV. It has been studied intensively over the last years due to the possible applications in optoelectronic and electronic devices such as light emitting diodes [1], laser diodes [2], which are active in the green, blue and ultraviolet wavelength, detectors [3] and high temperature/high power electronics [4]. C-plane GaN is the most common orientation to grow GaN devices. However, GaN suffers of polarization effects originating from c-[0001] polar axis of the wurtzite structure. These effects produce strong electric fields that affect the lifetime and efficiency of the devices. One approach to avoid this problem is to grow GaN as non polar structures (m-{1-100}[5] and a-{11-20} [6]) planes GaN. There is a considerable interest to analyze the defects in a-plane GaN layers and their effect in the optoelectronic properties of GaN-based devices that are grown on r-plane sapphire in non polar directions. This work presents the structural characterization by electron microscopy of a-plane GaN grown on r-plane sapphire.