Phase Separation Resulting from Mg Doping in p-InGaN Film Grown on GaN/Sapphire Template

The spontaneous formation of a two-layered structure in p-InGaN is observed with increasing Mg doping level. X-ray reciprocal space mappings reveal that the two layers are resulted from phase separation with different In contents and strain states. The bottom p-InGaN layer near the GaN template is totally strained with low-density dislocations, while the top layer is relaxed with high-density dislocations. The average In content in the relaxed layer is much higher than that in the totally strained one. The layered structure caused by phase separation is interpreted in terms of the compressive strain increase induced by Mg doping and the strain relaxation by dislocations.