Defect Creation in InGaAs/GaAs Multiple Quantum Wells - II. Optical Properties

The optical properties of three sets of InGaAs/GaAs multiple quantum well (MQW) structures grown by molecular beam epitaxy and previously characterized by x-ray diffraction for crystal perfection were investigated. The correlations between growth conditions, crystal defects, and optical properties are discussed. Evaluation of the relative importance of non-radiative Shockley-Read-Hall (SRH) recombination was carried out according to a method presented herein. The optimal deposition temperature was determined based on both proper carrier confinement in the nanostructures and the least non-radiative recombination. Growing below this temperature increased SRH-recombination whereas higher growth temperatures led to carrier localization in local band edge minima. Varying the MQW periodicity and MQW period allowed the study of their effects on the strength of SRH-recombination. MQW periodicity results are explained in the frame of a cumulative deterioration effect with continued epitaxial growth, while MQW period data shows correlations between relaxation of the initial elastic stress and SRH-strength. Limitations of the underlying model for SRH-analysis are pointed out.