Wafer-scale porous GaN single crystal substrates and their application in energy storage

Abstract

Porous GaN has recently attracted much interest due to its high surface area, shift of bandgap and efficient luminescence. However, the porous GaN materials obtained so far are mainly fabricated via an electrochemical etching or a photoelectrochemical etching method. Here, we report the fabrication of wafer-scale (2 inch) porous GaN by a novel and simple high temperature annealing process. A model is proposed, based on scanning electron microscopy as well as the stabilities of the GaN crystallographic plane, to explain the formation mechanism of the porous GaN. Improvement of the crystal quality, enhancement of the optical quality and strain relaxation of porous GaN are confirmed by the HRXRD, PL and Raman spectroscopy results. A three-electrode system based on the porous GaN electrodes is assembled. The good capacitive behavior and superior electrochemical reversibility validate the concept of porous GaN-based supercapacitors and point to their potential in energy storage applications.