Abstract
Two-dimensional (2D) materials such as graphene and transition-metal chalcogenides have been extensively studied because of their superior electronic and optical properties. Recently, 2D materials have shown great practical application in position-sensitive detectors (PSDs), originating from the lateral photoelectrical effect of the materials or junctions. The high position sensitivity and ultrafast photoresponse of PSDs based on 2D materials, especially compatibility with Si technology, may enable diverse optoelectronic applications. In this review, recent studies of PSDs based on 2D materials are summarized, providing a promising route for high-performance PSDs.
Highlights
Introduction Since Schottky andWallmark discovered and promoted the lateral photovoltaic effect (LPE) in p–n junctions[1], intensive research has been conducted on the LPE in diverse applications, including space exploration, environmental monitoring, and optical engineering
To achieve higher-performance position-sensitive detectors (PSDs), various strategies have been used with different 2D materials
By studying the low-energy consumption, high sensitivity, and ultrafast response sensing systems based on 2D materials such as graphene and transition sulfides, the physical mechanisms of the large LPE and ultrafast response time in the PSD were elucidated
Summary
The electron density N(r) can be derived as follows: jx À rj. NðrÞ 1⁄4 N0exp À λn ð3Þ where λn 1⁄4 pffiDffiffiffinffiffiτffiffinffiffi is the diffusion length, Dn 1⁄4 e2kρBNTF0 ; and ρ are the diffusion constant and resistivity of the n-type semiconductor, respectively; τn is the electron diffusion lifetime, NF0 1⁄4 83π À2mhe2EF0Á32 is the electron density below the Fermi level (EF0), and x is the position of the laser point. The Fermi level of an n-type semiconductor after laser irradiation at position r can be expressed as follows: EFnðrÞ 1⁄4 EF0 þ kBT NðrÞ ð4Þ nT where the electron density in the n-type semiconductor conduction band is nT 1⁄4 2ð2πmekBT Þ2 exp À EC À EF0. The PSDs based on 2D materials exhibit outstanding properties in a broadband wavelength range with a position sensitivity of up to 401 mV mm−1 43, ultrafast response time of less than 0.5 μs[43], nonlinearity of no more than ~2%44, and a power detection limit as low as ~17 nW6. Graphene-based devices typically exhibit excellent performance, such as a large photoresponsivity, a high detectivity, a great power conversion efficiency, and an ultrafast response speed. Wang et al reported a graphene-based PSD that can detect ultrafast weak signals because of the high mobility of graphene and long lifetime of photogenerated carriers at the interface of
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