Influence of nonstoichiometry on long-range order and its measurement in (GaAs)1−xGe2x and related alloys

Abstract

The influence of nonstoichiometry on long-range order in metastable alloys of GaAs with Ge has been studied using Monte Carlo simulations and analytic approximations based on the Davis–Holloway stochastic growth model applied to a 〈111〉 growth direction. The results show that the direct effects of nonstoichiometry on long-range order are relatively small. However, deviations from stoichiometry comparable to those reported previously can introduce significant errors into x-ray measurements of the order parameter. It is shown that discrepancies between measured order parameters and those calculated using the growth model can be explained as arising from the unrecognized effects of nonstoichiometry on the x-ray measurements. An incidental result of the analysis is that the long-range order predicted by the Davis-Holloway model arises entirely from its prohibition of Ga-Ga nearest-neighbor pairs. Identical results are obtained with and without the additional prohibition of As-As nearest-neighbor pairs.