Proton Implantation Mechanism in GaN Layer Transfer by Using the Ion-Cut Process

Abstract

The proton implantation condition for the ion-cut process in wurtzite-phase GaN and the associated mechanisms of surface blistering of GaN films were investigated. Etch-pit density (EPD) measurements, photoluminescence (PL) spectroscopy, and high resolution X-ray diraction (HRXRD) were used to investigate the crystalline quality of the as-grown GaN epi-wafers. The proton beam was implanted at 60 keV with fluences in the range of 3 5 ◊ 10 17 H + /cm 2 at room temperature. The influences of the crystallinity of the GaN wafers, the ion fluence and the post-implantation annealing conditions (200 450 C) on the blistering process were studied. Optical microscopy, field emission scanning electron microscopy (FE-SEM), HRXRD, Rutherford backscattering Spectrometry (RBS)/channeling (RBS/C), and cross-sectional transmission electron microscopy (XTEM) were used to investigate splitting kinetics, and the optimum conditions for achieving exfoliation only after post-implantation annealing were determined for the GaN ion-cut process. Our results suggest that the ion-cut process is sensitive to both the implant fluence and the annealing conditions, however, so far as the measured crystal quality is concerned, against our expectations, there was no notable influence on the blistering property. The optimum post-implantation annealing temperature was less than 350 C, and low temperature splitting is of importance for layer transfer between dissimilar materials with very dierent thermal expansion coecients.