Efficient Exciton Transfer from In_0.35Ga_0.65As Template into InAs Quantum Dots Grown on GaAs (311)B Substrates

Atomic force microscopy (AFM) and power-dependent micro-photoluminescence (μ-PL) spectroscopy are used to study the structure and exciton energy states in InAs quantum dots (QDs) grown on an In_0.35Ga_0.65As template on GaAs (311)B. The In_0.35Ga_0.65As template, consisting of a two-dimensionally modulated layer of closely packed connected cells, has a remarkable effect on the optical properties of the InAs QDs. By comparing the emission spectra of the samples without and with InAs QDs and the work carried out by Gong et al. [J. Cryst. Growth 251 (2003) 150; Appl. Phys. Lett. 81 (2002) 3254] we conclude that the existence of the In_0.35Ga_0.65As template enhances the photo-absorption and therefore the exciton emission from the QDs due to efficient exciton transfer from the template into the QDs. Furthermore, the PL emission from the QDs clearly reveals four discrete energy levels, S, P, D, and F with increasing excitation power.