Near-field Scanning Optical Microscopy and Electron Microprobe Microscopy Investigations of Immiscibility Effects in Indium Gallium Phosphide Grown by Liquid Phase Epitaxy

摘要

We have used Near-field Scanning Optical Microscopy (NSOM) and Electron Probe Microanalysis (EPMA) to study the topographic and microscopic optical properties of indium gallium phosphide (In_(1-x)Ga_xP) samples grown by Liquid Phase Epitaxy (LPE) on gallium arsenide substrates. Photoluminescence (PL) intensity images gathered using NSOM exhibit strong, highly localized variations in the optical properties of these samples that are seen to occur roughly in registry with the surface topography. Shifts in the PL peak position (by 27 meV) occur across highly mismatched samples with high In content, whereas no shifts were seen for In_(n-x)Ga_xP films with a nearly lattice matched composition. Compositional fluctuations lead to these PL peak energy shifts, measured by NSOM with a resolution of 250 nm. These composition fluctuations arise from the known solid-solid miscibility gap in the In_(1-x)Ga_xP system at temperatures used for the growth of these samples.