Proton irradiation induced defects in GaN: Rutherford backscattering and thermally stimulated current studies

Abstract

The proton irradiation induced defects in GaN are studied by combining elastic recoil detection analysis (ERDA), thermally stimulated current (TSC), and Rutherford backscattering spectroscopy (RBS) measurements. The proton irradiation (peak concentration: 1.0×1015cm−2) into GaN films with a thickness of 3μm is performed using a 500keV implanter. The proton concentration by a TRIM simulation is maximum at 3600nm in depth, which means that the proton beam almost passes through the GaN film. The carrier concentration decreases three orders of magnitude to 1015cm−3 by the proton irradiation, suggesting the existence of the proton irradiation-induced defects. The ERDA measurements using the 1.5MeV helium beam can evaluate hydrogen from the surface to ∼300nm. The hydrogen concentration at ∼220nm is ∼8.3×1013cm−2 and ∼1.0×1014cm−2 for un-irradiated and as-irradiated samples, respectively, suggesting that electrical properties are almost not affected by hydrogen. TSC measurements show a broad spectrum at around 110K which can be divided into three traps, P1 (ionization energy 173meV), P2 (251meV), and P3 (330meV). The peak intensity of P1 is much larger than that of P2 and P3. These traps are related to the N vacancy and/or complex involving N vacancy (P1), neutral Ga vacancy (VGa) (P2), and complex involving VGa (P3). The Ga displacement concentration evaluated by RBS measurements is 1.75×1019cm−3 corresponding to 1/1000 of the Ga concentration in GaN. The observed Ga displacement may be origins of P2 and P3 traps.