Effect of Be++O+ coimplantation on Be acceptors in GaN

P-type regions were produced in undoped GaN films by Be+ and Be++O+ implantation and subsequent annealing at temperatures between 1000 and 1050 °C. From thermal admittance spectroscopic measurements, the activation energy of the Be acceptor level was found to decrease from ∼240 to ∼163 meV by the implantation of additional O atoms, which is in reasonable agreement with the improvement in p-type doping characteristics determined by room-temperature Hall-effect measurements. These results indicate that Be++O+ coimplantation reduces the depth of the Be acceptor level based on a site-competition effect. Therefore, these acceptor levels are most probably attributable to Be atoms at interstitial and Ga-lattice sites.