Hybrid stranski-krastanov/submonolayer quantum dot heterostructure with type-II band alignment: an efficient way of near infrared photovoltaic energy conversion

Abstract

Photoabsorption throughout the entire solar spectrum and successive efficient photovoltaic energy conversion are always being the primary goal in the domain of solar energy conversion technology. Many strategies like multijunction, tandem, intermediate band, quantum dot/well, nanowire, plasmonic metasurface, organic-inorganic, etc., have been demonstrated to facilitate broadband absorption, starting from visible to near infrared (NIR) range. Here we have proposed a novel vertically coupled stranski-krastanov/submonolayer (SK/SML) quantum dot heterostructure with type-II band alignment for improved NIR photodetection. Standard III-As based PIN heterostructure facilitate with hybrid SK/SML quantum dot layers show broad NIR photo-absorption. Structural characteristic reveals improved material quality with reduced cumulative strain for 15 nm inter-dot barrier sample. Temperature/power dependent luminescence spectroscopy enlightens on the carrier transition mechanism. Thus explains the reason behind this broad NIR photo-voltage generation which is further clarified with device performance. Starting from this point, further theoretical investigation has been done to understand the effect of Sb incorporation in strain profile, band alignment, and absorption window. Finally, we have proposed a superior configuration for broad and tunable NIR photodetection.