Compensating point defects in He+4 -irradiated InN

We use positron annihilation spectroscopy to study 2 MeV He+4 -irradiated InN grown by molecular-beam epitaxy and GaN grown by metal-organic chemical-vapor deposition. In GaN, the Ga vacancies act as important compensating centers in the irradiated material, introduced at a rate of 3600 cm-1. The In vacancies are introduced at a significantly lower rate of 100 cm-1, making them negligible in the compensation of the irradiation-induced additional n -type conductivity in InN. On the other hand, negative non-open volume defects are introduced at a rate higher than 2000 cm-1. These defects are tentatively attributed to interstitial nitrogen and may ultimately limit the free-electron concentration at high irradiation fluences. © 2007 The American Physical Society.