Towards a better understanding of the operative mechanisms underlying impurity-free disordering of GaAs: Effect of stress

Abstract

The effect of stress on defect creation and diffusion during impurity-free disordering of SiOₓ-capped n-GaAs epitaxial layers has been investigated using deep level transient spectroscopy. The oxygen content in the SiOₓ layer and the nature of the stress that it imposes on the GaAs layer were varied by changing the nitrous oxideflow rate, N, during plasma-enhanced chemical vapor deposition of the capping layer. The peak intensity of defects S1 and S4 increased with the increasing nitrous oxideflow rate to exhibit a maximum in the range 80 sccm<N<200 sccm. Any further increase in N resulted in a decrease in peak defect intensity, which reached an almost constant value for N>350 sccm. On the other hand, the peak intensity of S2* increased linearly with N. We have explained the maximum in the intensity of defects S1 and S4 for 80 sccm<N<200 sccm to be due to a corresponding maximum in the compressive stress which is experienced by the capped GaAs layer during annealing. Although the creation of S2*, which we have proposed to be a complex involving the galliumvacancy(VGa), is enhanced with the increasing compressive stress, it also becomes efficiently converted into the arsenic-antisite, AsGa. The compound effect of these opposing mechanisms results in a linear dependence of the peak intensity of S2* on N. This study is to the best of our knowledge the first to provide the evidence for the stress-dependent anti-correlation between VGa- and AsGa-related defects in GaAs. We have also narrowed the origin of S1 to complexes involving arsenic interstitials, Asi, and/or AsGa.