Proton Irradiation Effects on AlGaN/AlN/GaN Heterojunctions

Abstract

AlGaN/AlN/GaN heterojunctions were irradiated by 3 MeV protons with different fluences. Hall and C-V measurements showed that the density and mobility of 2DEG for heterojunctions decreased after proton irradiation. The crystal quality and optical properties of AlGaN/GaN heterojunctions were characterized by the variations of the micro-Raman scattering spectra, XRD and photo luminescence (PL) spectra with proton fluence. It has been obtained that the strain and dislocation of GaN and AlGaN were not affected by the proton injected. The proton irradiation caused the increase of structural defects in HT-AlN buffer layer, which lead to the red shift of A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> (LO) mode. The higher tails of XRD rocking curve indicated the introduction of point defects by irradiation. The full-width at half-maximum (FWHM) of E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">high</sup> phonon mode broadened, which was consistent with change of FWHM of PL near-band-edge emission (BE). The spectra of yellow band normalized to the intensity of BE demonstrated a great increase of Ga vacancies related defects, which may be the main reason for the degradation of optical properties.