Optical properties of InxGa12xN alloys grown by metalorganic chemical vapor deposition

We present the results of optical studies of the properties of InxGa12xN epitaxial layers (0,x ,0.2) grown by metalorganic chemical vapor deposition. The effects of alloying on the fundamental band gap of InxGa12xN were investigated using a variety of spectroscopic techniques. The fundamental band-gap energies of the InxGa12xN 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 InxGa12xN 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. © 1998 American Institute of Physics. @S0021-8979~98!09520-6#