Optical properties of InxGa1−xN alloys grown by metalorganic chemical vapor deposition

We present the results of optical studies of the properties of InxGa1−xN epitaxial layers (0<x<0.2) grown by metalorganic chemical vapor deposition. The effects of alloying on the fundamental band gap of InxGa1−xN were investigated using a variety of spectroscopic techniques. The fundamental band-gap energies of the InxGa1−xN alloys were determined using photomodulation spectroscopy measurements and the variation of the fundamental band gap was measured as a function of temperature. The effects of pressure on the band gap for InxGa1−xN samples with different alloy concentrations were examined by studying the shift of photoluminescence (PL) emission lines using the diamond-anvil pressure-cell technique. The results show that PL originates from effective-mass conduction-band states. Anomalous temperature dependence of the PL peak shift and linewidth as well as the Stokes shift between photoreflectance and PL lines is explained by composition fluctuations in as-grown InGaN alloys.