Thermal Stress and Strain in a GaN Epitaxial Layer Grown on a Sapphire Substrate by the MOCVD Method

H. R. Alaei ； H. Eshghi ； R. Riedel ； D. Pavlidis

《Chinese Journal of Physics》 48卷3期 (2010/06) Pp. 400-407

並列摘要

In this article we have studied the existence of stress and strain in a Si-doped GaN (2μm)/sapphire structure grown by the metal-organic chemical vapour deposition (MOCVD) method and tried to model the parameters. The presence of stress in our sample is supported by an E2 Raman shift mode (Δω) of about 1.25 cm^(-1). To find the amount of biaxial basal plane stress we performed two techniques, XRD and film bending by a profilometer. The XRD technique confirmed that the GaN layer has a hexagonal structure with the lattice constants of c=5.1825Å and a=3.187Å. Our theoretical calculations show that this layer suffers a biaxial stress (σ(subscript α)) of about 0.175±0.003 GPa. The profilometer data analysis also leads to a compatible value of 0.12±0.04 GPa. These parameters altogether suggest the relation Δω=7.1±0.1σcm^(-1)/GPa for this layer.