Optical properties of In_xGa_1-xN alloys grown by metalorganic chemical vapor deposition

We present the results of optical studies of the properties of In_xGa_1-xN epitaxial layers (0≪x≪0.2) grown by metalorganic chemical vapor deposition. The effects of alloying on the fundamental band gap of In_xGa_1-xN were investigated using a variety of spectroscopic techniques. The fundamental band-gap energies of the In_xGa_1-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 In_xGa_1-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. © 1998 American Institute of Physics.