High-performance nonpolar a-plane GaN-based metal–semiconductor–metal UV photo-detectors fabricated on LaAlO3 substrates

Abstract

High-performance nonpolar a-plane GaN-based metal–semiconductor–metal (MSM) ultraviolet (UV) photo-detectors are fabricated based on high-quality nonpolar a-plane GaN epitaxial films grown on LaAlO₃(100) substrates. By effectively controlling the interfacial reactions between GaN and LaAlO₃(100) through low temperature growth by pulsed laser deposition, together with systematically studying the formation mechanism of GaN/LaAlO₃ hetero-interfaces by first-principles calculations, high-quality nonpolar a-plane GaN epitaxial films with no interfacial layer are obtained. The as-grown ∼300 nm-thick nonpolar a-plane GaN epitaxial films grown at a low temperature of 450 °C show high crystalline quality with the full-width at half-maximum values of 0.21° and 0.41° for GaN(11−20) and GaN(10−11) X-ray rocking curves, respectively; and a very smooth surface with a root-mean-square surface roughness of 1.2 nm. These high-quality nonpolar a-plane GaN epitaxial films are then fabricated into MSM UV photo-detectors, which reveal a high responsivity of 1.35 A W⁻¹ with a low dark current of 8.2 nA @ 5 V. These are the best values for nonpolar GaN-based MSM UV photo-detectors ever reported. These high-performance nonpolar a-plane GaN-based MSM UV photo-detectors have immense potential for application in UV warning and curing systems and light therapy devices.