Raman study of V/III flux ratio effect in InP/InAlAs/InP heterostructures grown by MOCVD

摘要

Micro-Raman measurements have been carried out in order to study the V/III flux ratio effect in InP/InAlAs/InP heterostructures grown by metal-organic chemical vapor deposition (MOCVD). Photoluminescence (PL) studies in InP/InAlAs/InP heterostructures~([1,2]) show a strong dependence of the PL band linewidth on V/III molar ratio. In addition to the observation of the two-mode behavior and the disorder activated modes in InAlAs alloy, an analysis of Raman spectra shows a line shape broadening and wavenumber shift of Raman peaks for various V/III molar ratios, with minimum linewidth and lattice mismatch occurring at V/III = 50. Also, a strong dependence on the composition modulation of the AlAs-like longitudinal optic (LO_(AIAs-like)) phonon was observed due to clustering. Calculation of the in-plane strain shows that the lattice mismatch between the epilayer and the substrate is relatively insensitive to flux ratio variation within the range investigated. Therefore, the high arsenic overpressures used have an insignificant adverse effect on the quality of the hetero-interfaces.