Optical study of phase-separated thick InGaN layers grown on a compliant substrate

The optical properties of thick InGaN layers grown on a compliant substrate (CS) were investigated. The CS was fabricated by thermal deformation of nanoporous GaN during high-temperature annealing. The strain sharing between the InGaN with CS was characterized using high-resolution X-ray diffraction, and we found a reduced in-plane strain of the InGaN on the CS. Photoluminescence (PL) spectra exhibited double peaks associated with discontinuous strain relaxation during the growth of the InGaN films. The strain sharing suppressed defect formation in the InGaN grown on CS, whereas the degree of indium fluctuation was similar because the phase separation resulted from spinodal decomposition. The temperature dependence of the PL spectra and internal quantum efficiency were analyzed as a function of the thickness of the InGaN layer. The effects of the CS on the growth of thick InGaN layers are discussed.