The effects of nitrogen ion sputtering and thermal anneal processing on the surface electronic structure of the ternary III–V semiconductor In0.12Ga0.88N have been studied using scanning photoemission microscopy. No phase separation of the material is observed for annealing temperatures up to 650 °C. However, samples annealed at 700 °C for 5 h show clear evidence of phase separation. Furthermore, annealing at these temperatures with the sample surface directly exposed to ultrahigh vacuum produces a surface greatly deficient in In and with considerable surface roughness. This can be circumvented by using a sacrificial sample in physical contact with the film to artificially increase the local vapor pressure of Ga, In, and N during annealing. © 2003 American Institute of Physics.