Ion-induced nitridation of GaAs(1 0 0) surface

The ion-induced nitridation of GaAs(1 0 0) using 1.2 keV N2+ ion beams has been investigated using in situ X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Ga-rich surfaces produced by Ar+ cleaning, promote initial nitridation and formation of GaN. The dependence of [N]/[Ga] and [As]/[Ga] atomic ratios on substrate temperature, nitridation time, and nitrided layer depth suggest that the process is self-limiting. The degree of nitridation increases with the temperature, but decreases again at higher temperatures (>450°C). Smooth nitrided layers are formed between room temperature and 450°C. For nitridation at T=600°C however, the aggregation of GaAs1−xNx results in the roughening of the nitrided surfaces. Diffusion, sputtering, and decomposition effects in the nitridation process are considered, and the mechanisms of GaAs1−xNx formation are discussed.