Colloidal III–V Quantum Dot Photodiodes for Short‐Wave Infrared Photodetection

Abstract

Short‐wave infrared (SWIR) image sensors based on colloidal quantum dots (QDs) are characterized by low cost, small pixel pitch, and spectral tunability. Adoption of QD‐SWIR imagers is, however, hampered by a reliance on restricted elements such as Pb and Hg. Here, QD photodiodes, the central element of a QD image sensor, made from non‐restricted In(As,P) QDs that operate at wavelengths up to 1400 nm are demonstrated. Three different In(As,P) QD batches that are made using a scalable, one‐size‐one‐batch reaction and feature a band‐edge absorption at 1140, 1270, and 1400 nm are implemented. These QDs are post‐processed to obtain In(As,P) nanocolloids stabilized by short‐chain ligands, from which semiconducting films of n‐In(As,P) are formed through spincoating. For all three sizes, sandwiching such films between p‐NiO as the hole transport layer and Nb:TiO2 as the electron transport layer yields In(As,P) QD photodiodes that exhibit best internal quantum efficiencies at the QD band gap of 46±5% and are sensitive for SWIR light up to 1400 nm.

Indium arsenide quantum dots: an alternative to lead-based infrared emitting nanomaterials

“…to reduce the concentration of monomers in order to achieve a larger nucleation radius) 105 eventually obtaining larger nuclei and consequently larger InAs QDs. 101 The resulting InAs QDs exhibited a band-edge absorption tunable from 1140 nm to 1400 nm with relatively broad HWHM (∼150 meV).…”

“… 97 In another study, the same group replaced the native, long-chain OAm ligands by a combination of short-chain stabilizers such as n -butylamine and 3-mercapto-1,2-propanediol to enhance the inter-dots charge carrier mobility. 101 Recently, Zhu et al revealed that most of the InAs trap states originate from surface indium vacancies. These can be partially passivated by zinc chloride (ZnCl 2 ) acting as Z-type ligands ( Fig.…”

Development of Group III–V Colloidal Quantum Dots for Optoelectronic Applications

“…Furthermore, state-of-the-art surface treatment has driven infrared photodetection. Figure e and f show the InAs CQD-based photodetector targeting 900 to 1400 nm, respectively. , Besides, group III–V CQDs have also been applied in various fields, such as down-conversion, LEDs, and lasers. ,, Beyond the visible-range LEDs with InP core/shell structure, a NIR-range LED using InAs core/shell has been studied and recently reported a quantum yield of 73% with device EQE of 13% . However, remaining unresolved challenges limit the progress in achieving advanced optoelectronic devices.…”

“…61−64 However, the resulting device often suffered from poor stability and undesired trap states, which limited its further use in various optoelectronic applications. 64,65 The development of strategies for fabricating conducting films is on course, where films fabricated using halide or short organic ligands 22,56,63 with or without fluoride pre-treatment 66 exhibit a mobility of about 10 −2 −10 −5 cm 2 /(V•s). The modest conductivity of group III−V CQD films compared to films of other ionic CQDs or bulk materials may come from the high trap density in the former.…”

“…For example, commercialized group III−V InGaAs photodetector achieved a detectivity of 10 12 10 9 Jones for wavelength of 1400−1550 nm detection. 3,22 In addition, bulk GaAs solar cell recorded efficiency of about 30% while other group III−V CQD solar cells reported efficiency of about 1%. 23,24 We believed that the low performance of group III−V CQD-based optoelectronic device is originated from the underdeveloped material synthesis and surface engineering strategy in III−V CQDs.…”