Photoreflectance investigations of energy level structure of InAs quantum dashes embedded in InGaAs/InGaAlAs quantum well grown on InP substrate

摘要

Photoreflectance (PR) and photoluminescence measurements have been performed on molecular beam epitaxy grown InAs quantum dashes (QDash) of various sizes, embedded in In_(0.53)Ga_(0.47)As/ In_(0.53)Ga_(0.23)Al_(0.24)As quantum well (QW), grown on InP substrate. PR response from all relevant parts of the structure, i.e InAs/In_(0.53)Ga_(0.47)As QDashes, InAs/In_(0.53)Ga_(0.47)As/In_(0.53)Ga_(0.23)Al_(0.24)As QW, and In_(0.53)Ga_(0.23)Al_(0.24)As barriers, has been obtained. The lowest energy transition related to the ground state transition in QDashes shifts towards red with the increase in QDash sizes (amount of deposited InAs material) reaching wavelengths longer than for structures without the intermediate QW. The experimental data on the energies of optical transitions combined with the numerical calculation within the effective mass approximation has allowed determining the energy level structure of the entire system, including the values of conduction band offset between InGaAs and InGaAlAs layers.