Effects of gas-flow sequences on the self-limiting mechanisms of GaAsN films grown by atomic layer epitaxy

Abstract

We adapted the atomic layer epitaxy (ALE) technique to grow GaAsN thin films. The effects of the gas flow sequences used on the self-limiting mechanism (SLM), the N incorporation ratios, and the concentrations of residual impurities were investigated. A pulse of the N precursor (monomethylhydrazine) was added after that of the Ga precursor (trimethylgallium) or the As (trisdimethylaminoarsenic) precursor, which were part of the conventional sequence used for the growth of GaAs films via ALE. If it was noticed that the SLM was in effect, the N precursor was supplied on the Ga- or As-terminated surface (the corresponding sequences and their resulting films are labeled as On-Ga and On-As, respectively). The On-As film exhibited rough surfaces, nonuniform N concentration, and disordered lattices owing to defects. On the other hand, in the case of the On-Ga sequence, GaAsN films with high-quality crystals were grown with the SLM in effect and the concentration of N being a few percent. The concentrations of the residual impurities (C and H) in the On-Ga film were low. This demonstrated that the On-Ga sequence was effective for growing GaAsN thin films on precisely controlled surfaces using the ALE technique.