Visible photoluminescence from self-assembled InAs quantum dots embedded in AlAs cladding layers

Photoluminescence (PL) from InAs self-assembled quantum dots (QD) embedded in the AlAs matrix was strong and clean around 700 nm. PL efficiency remained quite high at room temperature compared to other QD systems embedded in GaAs cladding layers. Transmission electron microscope pictures from the structure showed a clear formation of relatively small and coherently strained InAs QD. The observed blueshift with accompanying broadening of PL spectra with the increase of excitation power is interpreted in terms of local carrier tunneling in a dense QD system. The PL peak redshift with the increase of temperature was very large, as much as 228 meV. The anomalous shift is interpreted as due to activation-energy differences between dots of different sizes.