Negative Photoconductive Effects in Uncooled InAs Nanowire Photodetectors

Abstract

One-dimensional, direct, and narrow band gap indium arsenide (InAs) nanowires (NWs) have been emerging with great potentials for the next-generation wide-spectrum photodetectors. In this study, metal–semiconductor–metal (MSM) structure InAs NW-based photodetectors were fabricated by transferring MBE-grown NWs onto a sapphire substrate via a mechanical stamping method. These NW detectors exhibit strong negative photoconductive (NPC) effects, which are likely caused by the carrier dynamics in the “core-shell” structure of the NWs. Specifically, under the irradiation of a 405 nm violet laser, the maximum Idark/Ilight ratio reaches ∼102 and the NPC gain reaches 105 at a low bias voltage of 0.2 V. At room temperature, the rise and decay times of InAs NW devices are 0.005 and 2.645 s, respectively. These InAs NW devices with a high Idark/Ilight ratio and NPC gain can be potentially used in the field of vis/near-IR light communication in the future.

Sulfur-Passivated InSb Nanowires for Infrared Photodetectors

“…Due to the NPR effect, all of the I−T curves dropped to the closed state ("off") when the light was turned on and returned to the initial state ("on") when the light was turned off. 13,28,29,31 The good reproducibility and stability of I−T curves are strong demonstrations of the NPR properties to 1.06 μm incident light. For 1.55 μm incident light (Figure 4g), the I−V curve also decreased gradually when the incident power density increased from 0 to 9 mW mm −2 , again exhibiting typical NPR performance.…”

“…In Figure e, the time-resolved photoresponse represented by I – T curves was measured by periodically (20 s) switching the 1.06 μm light on and off with various power intensities of 1, 4, and 8 mW mm –2 at 0.1 V bias. Due to the NPR effect, all of the I – T curves dropped to the closed state (“off”) when the light was turned on and returned to the initial state (“on”) when the light was turned off. ,,, The good reproducibility and stability of I – T curves are strong demonstrations of the NPR properties to 1.06 μm incident light. For 1.55 μm incident light (Figure g), the I–V curve also decreased gradually when the incident power density increased from 0 to 9 mW mm –2 , again exhibiting typical NPR performance.…”

“…The photodetector possessed stable NPR performances toward incident infrared light, and the key parameters of responsivity ( R λ ) and external quantum efficiency (EQE) were calculated to be 123.46 A/W and 14,400% for 1.06 μm light, respectively, 59.26 A/W and 5610% for 1.31 μm light, respectively, and 120.99 A/W and 9680% for 1.55 μm light, respectively. Compared with InSb NWs reported in the literature, the S-InSb NWs prepared in this work have the highest room-temperature mobility and superior infrared photoresponse properties. − To reveal the origin of the NPR properties, an analysis of excited electron states in the band structure was performed under light illumination, and the NPR properties were found to stem from the photogating effect of the Sb–S layer on the S-InSb NW surface. ,− …”

“…With intriguing properties in terms of high carrier mobility, highly efficient photoelectric conversion, and suitability for braiding array devices, narrow bandgap III–V semiconductor nanowires (NWs) have aroused enormous amounts of research interest. − Among all binary III–V semiconductors, InSb NWs possess the narrowest bandgap (0.17 eV) and the highest electron mobility, along with a large Landé g-factor and strong spin–orbit interactions, making them technologically significant. ,− These materials are deemed to be suitable platforms for the study of topological superconducting quantum devices, Majorana zero modes, high-performance field-effect transistors (FETs), and especially infrared optoelectronic devices. − ,, …”

“…The challenges related to the growth of InSb NWs primarily stem from the large lattice parameters that inhibit their epitaxial growth on other III–V semiconductors. ,, According to the literature, InSb NWs have been commonly grown on an InSb wafer substrate , or on top of other NWs with a high tolerance for lattice mismatches, such as InP, InAs, etc. ,,, Additionally, due to the low vapor pressure and the surfactant effect of the Sb atom, Sb tends to aggregate on the NW surface, resulting in the deterioration of the surface states density. ,, Thus, the infrared photoresponse performances of the InSb NWs have rarely been studied. Notably, an intrinsic negative photoresponse (NPR) property has been identified for other narrow bandgap NW-based photodetectors. ,− In contrast with the common positive photoresponse (PPR), the NPR behavior means that the photocurrent will gradually decrease, or even fade away, with an increase in the external excitation light power. This phenomenon arises from excited electrons trapped by native surface defects, similar to a photogating layer (PGL). − The specific optoelectronic properties of InSb NWs remain to be uncovered.…”