Effect of InGaN/GaN Superlattice on Lattice Curvature of GaN Layers Grown on Sapphire Substrates

Abstract

The lattice curvature due to the difference in the thermal expansion coefficients between sapphire and GaN decreases the device performance and production yield. There is room to improve the lattice curvature and radius of curvature of GaN layers grown on sapphire substrates. Herein, an InGaN/GaN superlattice (SL) is grown on a low‐temperature GaN buffer layer through metalorganic vapor‐phase epitaxy to improve the lattice curvature. The lattice curvature of the GaN layer is investigated in terms of In content of the InGaN layer, the number of SL layers, cap layer, and GaN thickness. The radius of curvature increases with the increase in the number of SL layers and In content. The radius of curvature is 45 m when a 10‐period SL structure is used and the In content is 23.4%. When using a 20‐period SL structure, the GaN layer partially separates despite its very low thickness (2 μm). The improvement in the lattice curvature can be attributed to the thermal decomposition of InGaN during the annealing process from the growth temperature of InGaN to that of GaN.