A comprehensive analysis of strain profile in the heterogeneously coupled Stranski-Krastanov (SK) on Submonolayer (SML) quantum dot heterostructures

Abstract In this study, we demonstrate a detailed strain analysis of the heterogeneously coupled Stranski Krastanov (SK) on Submonolayer (SML) InAs quantum dot heterostructures with higher (0.1 ML/s) and lower (0.05 ML/s) growth rate of InAs. This hybrid structure utilizes advantages of both SK and SML QDs, and facilitates superior characteristics in the near-infrared energy harvesting. The spacer layer thickness between SK and SML QDs have been varied as 5, 7.5 and 10 nm to modulate the coupling between them and to get a better insight of the strain profile. Such strain modulation inside the heterostructure significantly affects the dot density and dot size distribution and thereby would ultimately impact the optoelectronic properties. It was observed that with increased spacer layer thickness, there was decrement in both in-plane and out-plane strain distribution within the entire heterostructure. The strain field obtained from the theoretical simulation of SK on SML QD structures supported the experimental results. In addition, the quantum dot infrared photodetector has been fabricated utilizing the optimized SK on SML QD heterostructure with the spacer layer thickness of 7.5 nm, which provided spectral response in the range of 2–6 μm and lower dark current as low as 1.05E-7 A/cm2 at 75 K at a bias of 1.5 V.