PROTON IRRADIATION INDUCED DEFECTS IN GaN SINGLE CRYSTAL FILM

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 into GaN single crystal films with a thickness of 3 μm is performed using a 500 keV implanter. The carrier concentration decreases three orders of magnitude to 10^15 cm^-3 by the proton irradiation. ERDA measurements using the 1.5 MeV helium beam can evaluate hydrogen. The hydrogen concentration at ～220 nm is ～8.3 × 10^13 cm^-2 and ～1.0 × 10^14 cm^-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 110 K which can be divided into three traps, P_1 (ionization energy 173 meV), P_2 (251 meV), and P_3 (330 meV). These traps are related to the N vacancy and/or complex involving N vacancy (P_1), neutral Ga vacancy (V_Ga) (P_2), and complex involving V_Ga (P_3). The Ga displacement concentration evaluated by RBS measurements is 1.75 × 10^19 cm^-3 corresponding to 1/1000 of the Ga concentration in GaN.