The effect of growth rate variation on structural and optical properties of self assembled InAs quantum dots

In spite of numerous advantages offered by Quantum Dot (QD) based imaging systems in infrared photo-detection, the physical realization of such systems has always been a challenging task. In this study, we aim to analyze the effects of growth rate variation on the structural and optical properties of self-assembled InAs/GaAs Stranski-Krastanov (SK) QDs grown on semi-insulating GaAs substrate using MBE (Molecular Beam Epitaxy). Five samples grown at a substrate temperature of 490 degrees C with varying growth rates (0.025ML/s, 0.05ML/s, 0.075ML/s, 0.1ML/s, 0.15ML/s) were investigated using PL spectroscopy, and AFM measurements. PL spectroscopy showed a blue shift in the ground state peak wavelength with an increase in growth rate which was further corroborated by AFM measurements, showing reduced dot-size with an increased growth rate. AFM measurements showed an increase in dot density with an increased growth rate suggesting increased tendency towards nucleation. Integrated PL intensity witnessed an initial increase with an increased growth rate before achieving its maxima for sample grown at 0.075ML/s, rendering the sample grown at 0.075ML/s best in terms of optical activity. These observations provided key insights into the growth kinetics operating during dot-formation through SK growth mode by evaluating the competition between the forces due to surface diffusion and nucleation.