Structure and electrical activity of rare-earth dopants in GaN

Density functional theory is used to investigate Eu, Er, and Tm rare earth (RE) impurities in GaN, paying particular attention to their structure, energetics, and electronic properties. The most stable site is when the RE is located at a Ga substitutional site but none of the defects possess deep energy levels. RE–VN close pairs are stable at temperatures greater than 1000 °C for 1 at. % RE doping and possess shallow levels possibly exciting intra-f luminescence in the visible. RE–VGa and RE-interstitial defects possess deep levels which exclude them as sources for visible RE-related luminescence.