Bi₂S₃Electron Transport Layer Incorporation for High-Performance Heterostructure HgTe Colloidal Quantum Dot Infrared Photodetectors

Abstract

Infrared photodetectors (PDs) based on epitaxial semiconductors occupy the majority of the market, but their high cost from material growth and device integration limits their application fields. Colloidal quantum dots (CQDs) provide a high potential candidate for infrared PDs due to their unique infrared sensitivity, tunable physical and chemical properties, and good compatibility with readout integration circuits. In particular, HgTe CQD PDs have demonstrated a wide detection range from shortwave to long-wave infrared. Although significant progress has been achieved in HgTe CQD infrared PDs, they are still in the primary stage of QD synthesis and prototype device fabrication. Here, we develop a new p−i−n photodiode from the traditional p−i device structure. Bismuth sulfide (Bi 2 S 3 ) films were adopted as the electron transport layer, which could favor uniform absorber deposition, superior charge extraction, and suppressed interfacial loss. The Bi 2 S 3 -based photodiodes have achieved a room-temperature dark current density as low as 1.6 × 10 −5 A/cm 2 at −400 mV. Furthermore, their specific detectivity (D*) achieves ∼10 11 Jones at room temperature.

On the Suitable Choice of Metal for HgTe Nanocrystal-Based Photodiode: To Amalgam or Not to Amalgam

“…To show the generality of the problem we aim to discuss, we start with the diode stack, which is currently the most used for HgTe NC-based devices, the latter being able to cover both short- − , and mid-wave infrared detection but also being used for electroluminescence . It consists of the combination of HgTe NCs with Ag 2 Te NCs, the latter being afterward cation exchanged to form a Ag-doped HgTe layer.…”

“…Usually, the choice of metal for a device is driven by its work function value for a proper ohmic contact design minimizing interface Schottky barriers. In this context, most diodes based on HgTe NCs as active material are currently combining gold as the hole extractor and a TCO as the electron extractor. − As a result, low work function metals are the ones of interest to extract electrons but are also the ones more prone to oxidize. In the specific context of mercury-based NCs, the high tendency of mercury to form amalgam raised another problem.…”

Multiresonant Grating to Replace Transparent Conductive Oxide Electrode for Bias Selected Filtering of Infrared Photoresponse

“…The ITO thickness (50 nm, Figure S3) was reduced compared to the typical one used in the visible region (180 nm range). At cryogenic temperature (80 K), the stack indeed behaves as a diode presenting a strongly rectifying behavior for the IV The successful character of this diode has been confirmed by its reuse within the following papers of the same group, 33,42 but also by others, 9,43,44 and can be considered as the most efficient platform for NC-based mid-IR sensing to date. In spite of this success, the use of ITO remains a clear issue; see Figure 1d−f.…”

Inside a nanocrystal-based photodiode using photoemission microscopy

“…Ackerman et al 24 were the first to propose the coupling of an HgTe NC layer with an Ag 2 Te layer, the latter being used as a hole extraction layer. Since then, many derivatives have been considered, in particular through the addition of an electron transport layer (Bi 2 S 3 , 25 CdSe, 26 SnO 2 27 ), confirming the potential of this specific diode stack for HgTe NC-based infrared sensing. To move beyond the already explored structures while avoiding an inefficient trial-and-error approach, deeper knowledge of the electronic structure must be correlated with the development of new diode stacks.…”