Optical spectra and phase separation effects in relaxed InGaAs grown by MOVPE method

The existence of InGaAs₂ and GaAs phases in In_xGa_1-xAs (x ~ 0.1–0.2) have been established from Raman scattering (RS) and infra red reflectivity (IR) spectra. The evidence of partial ordering of InGaAs₂ phase into [001]-(InAs)₁(GaAs)₁ monolayer superlattice have been obtained. The measurement of the free-carrier dependence of In_xGa_1-xAs electron effective masses from plasmon RS revealed decreasing of the nonparabolicity of the conduction band compared with the predictions of Kein model. Growth temperature induced band gap lowering and absorption edge splitting have been observed in photoluminescence (PL) and optical absorption (OA) spectra of In_xGa_1-xAs. The possible origin of the observed band gap anomaly is exciton localisation at InGaAs₂-phase size fluctuations.