<i>In situ</i> measurement of AlxGa1−xAs growth rate and composition by magnification inferred curvature method

Abstract

The direct in situ measurement of group-III element growth rates in epitaxial methods has been a continuous pursuit. Despite the development of numerous in situ monitoring tools, the accurate measurement of growth rates remains challenging. The calibration of group-III element fluxes, and consequently the associated growth rate, is performed through various methods (such as RHEED oscillations, beam equivalent pressure measurement, optical methods, and quartz crystal microbalance). However, these direct in situ measurements are often valid only under specific conditions and/or involve indirect measurements that require knowledge of additional parameters. In this study, we applied the magnification inferred curvature method (MIC) to directly measure the growth rate of slightly strained AlAs layers grown on GaAs substrates, and thus enabling calibration of the Al effusion cells and controlling the thickness and composition of pseudomorphic AlxGa1−xAs layers independently of their thickness, and the growth conditions. From MIC measurements, we were able to deduce the elastic parameters at growth temperature, enabling us to achieve a reliable and transferable calibration of the Al incorporation rate under defined experimental conditions. This calibration is mainly applicable to pseudomorphic epitaxial materials with low lattice mismatch, such as several III–V and II–VI alloy systems, provided they remain in the elastic deformation regime. Under these strict pseudomorphic growth conditions, the calibration remains fully transferable from one epitaxy chamber to another.