Ligand-Engineered HgTe Colloidal Quantum Dot Solids for Infrared Photodetectors

Abstract

HgTe colloidal quantum dots (CQDs) are promising absorber systems for infrared detection due to their widely tunable photoresponse in all infrared regions. Up to now, the best-performing HgTe CQD photodetectors have relied on using aggregated CQDs, limiting the device design, uniformity and performance. Herein, we report a ligand-engineered approach that produces well-separated HgTe CQDs. The present strategy first employs strong-binding alkyl thioalcohol ligands to enable the synthesis of well-dispersed HgTe cores, followed by a second growth process and a final postligand modification step enhancing their colloidal stability. We demonstrate highly monodisperse HgTe CQDs in a wide size range, from 4.2 to 15.0 nm with sharp excitonic absorption fully covering short- and midwave infrared regions, together with a record electron mobility of up to 18.4 cm2 V–1 s–1. The photodetectors show a room-temperature detectivity of 3.9 × 1011 jones at a 1.7 μm cutoff absorption edge.

Ultrafast Charge Carrier Dynamics and Transport Characteristics in HgTe Quantum Dots

“…While the field of HgTe quantum dot (QD) colloidal chemistry that started back in the 90s in Horst Weller’s group , is well developed nowadays and has come to provide synthetic recipes for a wide range of QD sizes and thus tunable emission wavelengths up to the mid-infrared (IR) range, − the research focus has shifted more toward IR-device engineering aspects. Various approaches have been implemented to obtain high-performance optoelectronic devices, such as coupling with plasmonic structures, − ligand engineering, surface chemistry control, , a more sophisticated development of the architecture of the device itself, − and so on. During the past 20 years the field of IR optoelectronic devices based on HgX (X = S, Se, Te) colloidal QDs has experienced impressive developments. , Up to date photodetectors with a responsivity up to 10 6 A/W and detectivity of 10 12 Jones beyond 2 μm have been reported. ,, Recently, by combining HgTe QDs and graphene, the sensitivity of phototransistors was greatly improved at wavelengths up to 3 μm .…”

“…During the past 20 years the field of IR optoelectronic devices based on HgX (X = S, Se, Te) colloidal QDs has experienced impressive developments. 18,19 Up to date photodetectors with a responsivity up to 10 6 A/W and detectivity of 10 12 Jones beyond 2 μm have been reported. 17,20,21 Recently, by combining HgTe QDs and graphene, the sensitivity of phototransistors was greatly improved at wavelengths up to 3 μm.…”

Material Perspective on HgTe Nanocrystal-Based Short-Wave Infrared Focal Plane Arrays

“…As a zero-band-gap semiconductor, HgTe − offers a particularly broad tunability in the infrared with optical features varying from the visible to the THz range . This has enabled the integration of HgTe as an optically active material in an extensive range of devices such as light-emitting diodes (LEDs), − lasers, − photonic structures, − infrared sensors, − and cameras . Following their use as light downconverters in displays and farming, nanocrystals are now being integrated into infrared cameras, − one of the first commercial applications in which the material is both electrically and optically active.…”

Extracting Bulk-like Semiconductor Parameters from the Characterization of Colloidal Quantum Dot Film Photoconductors

“…The nonaggregated HgTe CQDs are synthesized following Lan and co-workers. 36 A TEM image of the HgTe CQDs is shown as an inset in Figure 1a. The substrate is an interdigitated Pt electrode with a gap of L = 10 μm, evaporated on 300 nm of SiO 2 on doped Si.…”

“…The system studied is a film of mid-IR HgTe CQDs deposited on interdigitated electrodes. The nonaggregated HgTe CQDs are synthesized following Lan and co-workers . A TEM image of the HgTe CQDs is shown as an inset in Figure a.…”