Comprehensive investigation of polish‐induced surface strain in ⟨100⟩ and ⟨111⟩ GaAs and InP

摘要

This paper presents the results of a systematic and extensive investigation of polish‐induced surface strain in ⟨100⟩ and ⟨111⟩ GaAs and InP using Raman scattering from the longitudinal optical (LO) phonon modes. By using various lines of an Ar‐ion laser it was possible to accomplish nondestructive depth profiling. To account for the observed line‐shape changes we have used a model which is based on the convolution of the penetration depth of the light and skin depth of the polish‐induced surface strain. From such an analysis we have obtained the polish‐induced surface strain, skin depth of the strain, and inhomogeneous broadening. For the ⟨100⟩ surface, the strain is about 2–3 in both materials and the skin depth (100–500 A˚) is relatively independent of particle size. In contrast, for the ⟨111⟩ surface, the average surface strain is only about 0.6 for GaAs and 1.2 for InP and the skin depth is of the order the particle size. The dependence of the strain skin depth on polish time also has been studied. A qualitative argument based on polish‐induced bond breaking is proposed to explain why surface strain for ⟨111⟩ is considerably less than for ⟨100⟩ and why the strain is compressive for both surfaces. Using a one‐dimensional diffusion model, we can successfully explain the depth dependence of the polish‐induced strain and the polish time dependence of the damage skin depth. This analysis yields a diffusion coefficient for the polish‐induced strain for the two surfaces. Our diffusion model is consistent with the conventional model of chemomechanical polishing of compound semiconductors.