Strong enhancement of photoresponsivity with shrinking the electrodes spacing in few layer GaSe photodetectors

Abstract

A critical challenge for the integration of optoelectronics is that photodetectors have relatively poor sensitivities at the nanometer scale. Generally, a large electrodes spacing in photodetectors is required to absorb sufficient light to maintain high photoresponsivity and reduce the dark current. However, this will limit the optoelectronic integration density. Through spatially resolved photocurrent investigation, we find that the photocurrent in metal-semiconductor-metal (MSM) photodetectors based on layered GaSe is mainly generated from the region close to the metal-GaSe interface with higher electrical potential. The photoresponsivity monotonically increases with shrinking the spacing distance before the direct tunneling happens, which was significantly enhanced up to 5,000 AW−1 for the bottom Ti/Au contacted device. It is more than 1,700-fold improvement over the previously reported results. The response time of the Ti/Au contacted devices is about 10–20 ms and reduced down to 270 μs for the devices with single layer graphene as metallic electrodes. A theoretical model has been developed to well explain the photoresponsivity for these two types of device configurations. Our findings realize reducing the size and improving the performance of 2D semiconductor based MSM photodetectors simultaneously, which could pave the way for future high density integration of optoelectronics with high performances.

A study of lateral Schottky contacts in WSe2 and MoS2 field effect transistors using scanning photocurrent microscopy

“…When the laser is incident in the source depletion region of the device, the I ds -V ds curve exhibits a rectifying behavior. 29 To further investigate the modulation of the lateral depletion region length by V ds more directly, we also performed the SPCM studies on another FET device fabricated with a MoS 2 flake of 2.8 nm thick, as shown in Fig. At positive V ds , the source Schottky contact is reverse biased.…”

Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors

“…The Schottky barrier located at contact area can accelerate the separation of photogenerated electron-hole pairs and thus benefi t to photocurrent and also response rate. [ 43,46 ] In summary, for the fi rst time we demonstrated the synthesis of high-quality ultrathin few-layered single-crystalline SnSe 2 fl akes, might enriching the family of 2D semiconducting materials, via an improved CVD method and explored their applications in photodetectors. The utilization of low melting point iodide facilitates the formation of ultrathin …”

High‐Performance, Self‐Driven Photodetector Based on Graphene Sandwiched GaSe/WS2 Heterojunction

“…[5][6][7] Recently, the emergence of graphenelike semiconducting materials including black phosphorus, [8] transition metal dichalcogenides (TMDCs), [9,10] GaSe, [11,12] and InSe [13] have well remedied the zero-bandgap disadvantage and attracted tremendous attention. [5][6][7] Recently, the emergence of graphenelike semiconducting materials including black phosphorus, [8] transition metal dichalcogenides (TMDCs), [9,10] GaSe, [11,12] and InSe [13] have well remedied the zero-bandgap disadvantage and attracted tremendous attention.…”

“…The photoresponsivity stays a relatively high value over a range λ = 270-740 nm at V ds = −2 V. Interestingly, due to the existing of the built in electrical field between the p-GaSe and n-WS 2 , the device also shows sizeable photoresponsivity at V ds = 0 V over a wavelength range of λ = 270-680 nm, indicating that the device can work in extreme conditions. The characteristic absorption peak located at 410 nm corresponds to the transition from p x and p y -like orbits to the conduction band in the GaSe layer, [12] the other two peaks located at 520 and 630 nm arise from optical transitions involving a spin-orbit split valence band and degenerate conduction band at the K point of the Brillouin zone in the WS 2 layer. We have performed the measurements of photoresponsivity as a function of illumination wavelength with wavelength interval of 10 nm for the new device, as shown in Figure S2 of Supporting Information.…”