Effect of ex-situ annealing on coupled hybrid InAs Stranski-Krastanov (SK) on Submonolayer (SML) Quantum Dot heterostructures with different spacer layer thickness

Abstract

The strain-coupled InAs Stranski-Krastanov (SK) and submonolayer (SML) quantum dot (QD) heterostructure improves the optoelectronic properties of the infrared photodetector as compared to the single SK or SML heterostructures. The discussed heterostructures for SK on SML are grown with three different spacer layer thicknesses (5, 7.5 and 10 nm) between SK and SML dots and each sample is grown with two different growth rates (0.1 ML/sec and 0.05 ML/sec). In this study, we are modulating the optical and structural properties of the heterogeneously coupled SK on SML structure with ex-situ annealing treatment. Rapid thermal annealing at 650 ℃ and 700 ℃ is done for all samples. Photoluminescence (PL) result shows blue shift in the peak position for annealed samples compared to the as-grown samples. The reason for this blue shift can be (1) In out-diffusion from the dots, or (2) Diminution in dot size. A reduction in full width half maxima (FWHM) of the PL spectra along with the annealing temperature is observed, which confirms the smaller size of dots after annealing. Additionally, substantial variation in strain profile for these hybrid structures has been discerned by high resolution X-ray diffraction (HRXRD). Hence, this study would definitely help to optimize the ex-situ annealing temperature on heterogeneously coupled SK-SML structure for wavelength tunable photodetection in the near infrared regime.