Growth and Optical Properties of Double Heterostructure GaN/InGaN/GaN Films with Large Composition

The double heterostructure GaN/InGaN/GaN films with different thickness of the InGaN layer were grown at 780°C or 800°C by metal-organic chemical vapor deposition. The samples were investigated using x-ray diffraction (XRD), room-temperature photoluminescence (PL) and Raman scattering. The dependences of the samples on both the growth temperature and the thickness of the InGaN layer were studied. The composition of InGaN was determined by the results of XRD, and the bowing parameter of InGaN was calculated in term of the PL spectra. When the thickness of the InGaN layer was reduced, the phase separation of InGaN was found in some samples. The Raman frequency of A₁ (LO) and E₂ (low) modes in all the samples shifted and did not agree with Vegard's law.