HgTe colloidal quantum dot photodetectors using SnO2 as an electron transport layer

Solution-processed colloidal quantum dots (CQDs) photodiodes present a viable approach for monolithic integration of high-resolution, low-cost infrared imagers when paired with silicon readout circuits. Among CQDs materials, mercury cadmium telluride (HgTe) stands out as especially important for photodetectors due to its outstanding broadband infrared detection capabilities. Although zinc oxide (ZnO) is commonly used as an efficient electron transport layer in HgTe-based heterojunction devices, it encounters energy band misalignment issues with narrow-bandgap CQDs as the detection wavelength shifts toward longer infrared regions. To overcome this drawback, we introduce a novel top-emitting structure that substitutes the traditional sputtered ZnO layer with an atomic-layer-deposited SnO₂ layer. This approach ensures both improved energy band alignment and superior heterointerface quality. The fabricated photodiode delivers broadband response performance, achieving a peak room-temperature detectivity of 4.2×10¹¹ Jones and an extended cutoff wavelength of 1800 nm.