Study of the mechanisms of GaN film growth on GaAs surfaces by thermal and plasma nitridation

Abstract

The kinetics of GaAs nitridation using N2 plasmas, both radio frequency and electron cyclotron resonance sources, is investigated using in situ and real time ellipsometry. A comparison of plasma nitridation with the more conventional NH3 thermal nitridation of GaAs is also reported. We report that all the GaAs nitridation processes are self-limiting yielding only very thin GaN layers. The dependence of GaN layer thickness on surface pretreatment, surface temperature and N atom density in the plasma is reported. Smooth and stoichiometric GaN layers are formed at T<600 °C, whereas nitridation at T⩾600 °C yields rough and Ga-rich GaN layers. In both cases, it is shown that As segregates at the GaAs/GaN interface, indicating that GaAs plasma nitridation kinetics is limited by outdiffusion of As and/or AsN species.