Photoluminescence study and parameter evaluation in InAs quantum dot-in-a-well structures

The photoluminescence (PL), its temperature and power dependences have been studied in InAs quantum dots (QDs) embedded in the symmetric In0.15Ga0.85As/GaAs quantum well (QW) with QDs grown at different temperatures (470–535 °C). The ground state (GS) PL peaks shift with increasing QD growth temperatures: the red shift is observed when temperature increased from 480 to 510 °C and the blue shift is typical when the temperature raised from 510 to 535 °C. The fitting procedure (on the base of Varshni relation) has been applied to the analysis of GS PL peak positions versus temperatures. Obtained fitting parameters are compared with corresponding data for the temperature variation of energy band gap in the bulk InAs crystal and in the In0.21Ga0.79As alloy. The comparison has revealed that the structures with QDs grown at 490–510 °C have the same fitting parameters as the bulk InAs crystal. However in structures with QDs grown at the temperatures 470, 525 and 535 °C the fitting parameters testify that Ga/In inter-diffusion between QDs and a QW has been realized. It is shown that the Ga/In inter-diffusion process is accompanied by the appearance of nonradiative recombination defects.