Fast and Sensitive Colloidal Quantum Dot Mid-Wave Infrared Photodetectors

Abstract

Colloidal quantum dots (CQDs) with a band gap tunable in the mid-wave infrared (MWIR) region provide a cheap alternative to epitaxial commercial photodetectors such as HgCdTe (MCT) and InSb. Photoconductive HgTe CQD devices have demonstrated the potential of CQDs for MWIR photodetection but face limitations in speed and sensitivity. Recently, a proof-of-concept HgTe photovoltaic (PV) detector was realized, achieving background-limited infrared photodetection at cryogenic temperatures. Using a modified PV device architecture, we report up to 2 orders of magnitude improvement in the sensitivity of the HgTe CQD photodetectors. A solid-state cation exchange method was introduced during device fabrication to chemically modify the interface potential, leading to an order of magnitude improvement of external quantum efficiency at room temperature. At 230 K, the HgTe CQD photodetectors reported here achieve a sensitivity of 10 Jones with a cutoff wavelength between 4 and 5 μm, which is comparable to that of commercial photodetectors. In addition to the chemical treatment, a thin-film interference structure was devised using an optical spacer to achieve near unity internal quantum efficiency upon reducing the operating temperature. The enhanced sensitivity of the HgTe CQD photodetectors reported here should motivate interest in a cheap, solution-processed MWIR photodetector for applications extending beyond research and military defense.

Towards Infrared Electronic Eyes: Flexible Colloidal Quantum Dot Photovoltaic Detectors Enhanced by Resonant Cavity

“…The solution was precipitated with excess acetone and stored in chlorobenzene or tetrachloroethylene. 400 nm HgTe CQDs film was then drop‐casted as the sensing material . Thicker film gave stronger absorption, but longer transport length which led to lower collection efficiency.…”

“…The thickness had not been systematically optimized and further improvement of device performance was possible. Before depositing the top contact (5 nm Au), the HgTe CQDs film was doped with Ag 2 Te by a reported protocol . The fabrication of the Fabry–Perot started from depositing 50 nm Au on polyimide film.…”

“…The photocurrent was first amplified with a transimpedance amplifier and then amplified by a voltage amplifier. The noise was measured using a spectrum analyzer as reported in prior work …”

HgTe Nanocrystal Inks for Extended Short‐Wave Infrared Detection

“…Recently, mid‐wave infrared photodiodes, with high photoresponse (up to 0.8 A W −1 ), have been proposed by Guyot–Sionnest's group. Part of this success is based on the use of plasmon resonance to enhance the absorption of thin nanocrystal films with thicknesses below the absorption depth .…”

Designing Photovoltaic Devices Using HgTe Nanocrystals for Short and Mid‐Wave Infrared Detection

“…Hence, the dark current and its associated 1/ f noise are generally quite detrimental for the performance of the IR sensor device. This is why the most recent developments in the field have focused on designing devices operating in a photovoltaic mode . Here, we discuss recent progresses that have been obtained in our group in the extended short‐wave IR using interband transition in HgTe nanocrystals and in the mid‐wave IR relying on intraband transition in HgSe nanocrystals.…”