Comprehensive investigation of polish-induced surface strain in 〈100〉 and 〈111〉 GaAs and InP

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Abstract
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 Å) 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.