Effects of Rapid Thermal Annealing on the Optical Properties of InAs Quantum Dots with Asymmetric InGaAs Layers

Photoluminescence (PL) spectroscopy was used to investigate the effects of rapid thermal anneal- ing (RTA) on self-assembled InAs quantum dot (QD) structures having asymmetric In0.15Ga0.85As layers. After RTA, the PL spectra from the InAs QDs were blue-shifted and showed significant narrowing of the PL linewidth, compared with as-grown (unannealed) samples. In particular, the PL peak positions of the annealed QD samples, which had one InAs QD layer inserted between two In0:15Ga0.85As layers, were blue-shifted about 200 meV at annealing temperatures up to 750 ℃. This was about twice as large as the blue-shift observed for a QD sample with three InAs QD layers separated by an In0:15Ga0.85As/GaAs heteorostructure. The suppression of the blue-shift is attributed to reduced intermixing of indium atoms under the strain field within or nearby the QDs. The energy-level spacing between the ground states and the first excited states decreased as the annealing temperature was increased. This reduction in energy-level spacing is largely related to changes in the QD shape and size, especially changes in the aspect ratio (height/width) that result from annealing. KCI Citation Count: 0