A review on III-V compound semiconductor short wave infrared avalanche photodiodes.

The on-chip avalanche photodiodes (APDs) are crucial component of a fully integrated photonics system. Specifically, III-V compound APD has become one of the main applications of optical fiber communication reception due to adaptable bandgap and low noise characteristics. The advancement of structural design and material choice has emerged as a means to improve the performance of APDs. Therefore, it is inevitable to review the evolution and recent developments on III-V compound APDs to understand the current progress in this field. To begin with, the basic working principle of APDs are presented. Next, the structure development of APDs is briefly reviewed, and the subsequent progression of III-V compound APDs (InGaAs APDs, AlxIn1-xAsySb1-yAPDs) is introduced. Finally, we also discuss the key issues and prospects of AlxIn1-xAsySb1-ydigital alloy avalanche APDs that need to be addressed for the future development of ≥2µm optical communication field.

Fabrication of graphene: CdSe quantum dots/CdS nanorod heterojunction photodetector and role of graphene to enhance the photoresponsive characteristics.

Integration of graphene with semiconducting quantum dots (QDs) provides an elegant way to access the intrinsic properties of graphene and optical properties of QDs concurrently to realize the high-performance optoelectronic devices. In the current article, we have demonstrated the high-performance photodetector based on graphene: CdSe QDs/CdS nanorod heterostructures. The resulting heterojunction photodetector with device configuration ITO/graphene: CdSe/CdS nanorods/Ag show excellent operating characteristics including a maximum photoresponsivity of 15.95 AW-1and specific detectivity of 6.85 × 1012Jones under 530 nm light illumination. The device exhibits a photoresponse rise time of 545 ms and a decay time of 539 ms. Furthermore, the study of the effect of graphene nanosheets on the performance enhancement of heterojunction photodetector is carried out. The results indicate that, due to the enhanced energy transfer from photoexcited QDs to graphene layer, light absorption is increased and excitons are generated led to the enhancement of photocurrent density. In addition to that, the graphene: CdSe QDs/CdS nanorod interface can facilitate charge carrier transport effectively. This work provides a promising approach to develop high-performance visible-light photodetectors and utilizing advantageous features of graphene in optoelectronic devices.

Interlayer of PMMA Doped with Au Nanoparticles for High-Performance Tandem Photodetectors: A Solution to Suppress Dark Current and Maintain High Photocurrent.

Currently, colloidal quantum dots (CQDs)-based photodetectors are widely investigated due to their low cost and easy integration with optoelectronic devices. The requirements for a high-performance photodetector are a low dark current and a high photocurrent. Normally, photodetectors with a low dark current also possess a low photocurrent, or photodetectors with reduced dark current possess a reduced photocurrent, resulting in low detectivity. In this paper, a solution to suppress dark current and maintain a high photocurrent, i.e., use of poly(methyl methacrylate) doped with Au nanoparticles (NPs) (i.e., PMMA:Au) as an interlayer for enhanced-performance tandem photodetectors, is presented. Our experimental data showed that the dark current through the tandem photodetector ITO/PEDOT:PSS/PbS:CsSnBr3/ZnO/PMMA:Au/CuSeN/PbS:CsSnBr3/ZnO/Ag is suppressed significantly; meanwhile, a high photocurrent is maintained after a PMMA:Au interlayer has been inserted between two subdetectors. The inserted PMMA:Au interlayer acts as storage nodes for electrons, reducing the dark current through the device; meanwhile, the photocurrent can be enhanced under illumination. As a result, the specific detectivity of the tandem photodetector with 35 nm PMMA:Au interlayer was enhanced significantly from 5.01 × 1012 to 2.7 × 1015 Jones under 300 µW/cm2 532 nm illumination at a low voltage of -1 V as compared to the device without a PMMA:Au interlayer. Further, the physical mechanism of enhanced performance is discussed in detail.

Highly flexible memristive devices based on MoS2 quantum dots sandwiched between PMSSQ layers.

This paper reports a facile, cost effective method that uses an aqueous hydrothermal process for synthesizing two-dimensional molybdenum disulphide (MoS2) monolayer quantum dots (QDs) and their potential applications in flexible memristive devices. High-resolution transmission electron microscopy and atomic force microscopy images confirmed that the diameters of the synthesized MoS2 QDs with irregular shapes were in the range between 3 and 6 nm; their thicknesses were confirmed to lie between 1.0 and 0.8 nm, a clear indication that a monolayer of MoS2 QDs had been synthesized. Photoluminescence (PL) and time-resolved PL spectra of the MoS2 QDs revealed a strong emission in the blue region with a slower decay constant. Memristive devices fabricated by incorporating MoS2 QDs between poly(methylsilsesquioxane) ultrathin layers, which had been deposited on poly(ethylene terephthalate), demonstrated a high ON-OFF current ratio of ∼104, stable retention, and excellent endurance in the relaxed state; these devices were also demonstrated to function properly during bending and in a bent state. The flexible memristive devices demonstrated an OFF state with a very low current of 10-6 A. These results clearly show that ultrathin two-dimensional QDs have promising applications in high-performance flexible memristive devices.

Inkjet-Printed Photodetector Arrays Based on Hybrid Perovskite CH3NH3PbI3 Microwires.

Hybrid perovskite CH3NH3PbI3 has attracted extensive research interests in optoelectronic devices in recent years. Herein an inkjet printing method has been employed to deposit a perovskite CH3NH3PbI3 layer. By choosing the proper solvent and controlling the crystal growth rate, hybrid perovskite CH3NH3PbI3 nanowires, microwires, a network, and islands were synthesized by means of inkjet printing. Electrode-gap-electrode lateral-structured photodetectors were fabricated with these different crystals, of which a hybrid perovskite microwire-based photodetector would balance the uniformity and low defects to obtain a switching ratio of 16000%, responsivity of 1.2 A/W, and normalized detectivity of 2.39 × 1012 Jones at a light power density of 0.1 mW/cm2. Furthermore, the hybrid perovskite microwire-based photodetector arrays were fabricated and applied in an imaging sensor, from which the clear mapping of the light source signal was successfully obtained. This work paves the way for the realization of low-cost, solution-processed, and high-performance hybrid perovskite-based photodetector arrays.