InAs/GaAs Quantum Dots have piqued the interest of researchers owing to the advantages they offer in the fabrication of highly efficient optoelectronic devices. In this study, we aim to examine the consequence varying V-III ratio on optical and structural behavior of self-assembled InAs/GaAs Stranski-Krastanov (SK) Quantum Dots grown on GaAs substrate using Molecular Beam Epitaxy (MBE). Three samples consisting of three layers of vertically stacked Quantum Dots with three different V-III ratios (48, 60 and 80 respectively) grown at a substrate temperature of 490°C have been thoroughly examined using PL spectroscopy and HR-XRD. The best optical response is seen in the sample with 80 as VIII ratio. A higher As vapor pressure during growth seems to suppress the surface migration of Indium atoms leading to bigger dot size, increased PL intensity and more uniform distribution rendering better optical response. The absence of satellite peaks in HR-XRD measurements of sample with lower V-III ratio indicates significant density of point-defects. HRXRD analysis reveals an increase in perpendicular strain with greater V-III ratio. Reduced FWHM in sample with higher V-III ratio is in accordance with suppressed Indium diffusion and strain propagation across multi-layered nanostructure contributing to greater uniformity in dot-size. PL spectrum of sample with least V-III ratio shows sharp peaks around 900 nm indicating incomplete dot-formation at such low ratios leaving significant part of wetting layer exposed. Our investigation provides interesting insights into kinetics of nanostructure growth which will prove to be helpful in fabrication of optimized nanostructures.
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°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.