Extended Short-Wave Photodiode Based on CdSe/HgTe/Ag<sub>2</sub>Te Stack with High Internal Efficiency
Prachi Rastogi, Eva Izquierdo, Charlie Gréboval, Mariarosa Cavallo, Audrey Chu, Tung Huu Dang, Adrien Khalili, Claire Abadie, Rodolphe Alchaar, Stefano Pierini, Hervé Cruguel, Nadine Witkowski, James K. Utterback, Thibault Brulé, Xiang Xu, Philippe Hollander, Abdelkarim Ouerghi, Bruno Gallas, Mathieu G. Silly, Emmanuel Lhuillier
Abstract
Nanocrystal integration into focal plane arrays requires the development of new photodiode designs combining an efficient charge dissociation with a low dark current. Previously reported architectures based on HgTe/Ag2Te stacks appear to be suboptimal for cutoff wavelengths below 2.5 μm. Here, we show that the introduction of a thin and strongly coupled CdSe layer acting as an electron transport layer and a unipolar barrier drastically improves the electrical performances. This diode achieves a responsivity as high as 0.8 A W–1, corresponding to an internal efficiency above 90% for a 2 μm cutoff wavelength. The specific detectivity is close to 1011 Jones at room temperature and reaches 9 × 1011 Jones at 200 K, the highest value reported for a HgTe nanocrystal-based photodiode with operation around 2 μm. The diode time response can be as short as 200 ns and appears to be limited by band bending dynamics as revealed by time-resolved photoemission measurements.