Cross‐Substitution Promoted Ultrawide Bandgap up to 4.5 eV in a 2D Semiconductor: Gallium Thiophosphate

Abstract

vital importance in automatization, space and underwater communication, biological sterilization detection, and astronomical observation applications. [1][2][3][4][5] Wide bandgap semiconductors (WBSs) offer some obvious advantages over conventional silicon-based SBPDs and photomultiplier tubes due to their superior intrinsic properties including large bandgaps, high thermal stability, and excellent antiradiation characteristics. Therefore, the state-of-the-art SBPDs based on WBSs, such as SiC, diamond, [6] II-oxides, [7,8] and III-nitride materials, [9][10][11] serve as highperformance active layers and are widely reported. At the same time, these devices still have some challenges. For instance, the dangling bonds on such nonlayered WBSs may become trapping states or scattering centers, which hinder the effective transport of charge carriers in the channel and weaken the device performances. [5,12] Recently, the emergence of photodetectors based on 2D materials has opened up an avenue to circumvent the abovementioned dilemma owing to their free surface dangling bonds. [13,14] In addition, 2D materials usually have atomic thickness, [15] high specific surface area, [16] and strong light-matter interaction, [17] which can provide high responsivity and photoconductive gain in nanoscale photodetectors. [18][19][20][21][22] Such 2D materials Exploring 2D ultrawide bandgap semiconductors (UWBSs) will be conductive to the development of next-generation nanodevices, such as deep-ultraviolet photodetectors, single-photon emitters, and high-power flexible electronic devices. However, a gap still remains between the theoretical prediction of novel 2D UWBSs and the experimental realization of the corresponding materials. The cross-substitution process is an effective way to construct novel semiconductors with the favorable parent characteristics (e.g., structure) and the better physicochemical properties (e.g., bandgap). Herein, a simple case is offered for rational design and syntheses of 2D UWBS GaPS 4 by employing state-of-the-art GeS 2 as a similar structural model. Benefiting from the cosubstitution of Ge with lighter Ga and P, the GaPS 4 crystals exhibit sharply enlarged optical bandgaps (few-layer: 3.94 eV and monolayer: 4.50 eV) and superior detection performances with high responsivity (4.89 A W −1 ), high detectivity (1.98 × 10 12 Jones), and high quantum efficiency (2.39 × 10 3 %) in the solar-blind ultraviolet region. Moreover, the GaPS 4 -based photodetector exhibits polarization-sensitive photoresponse with a linear dichroic ratio of 1.85 at 254 nm, benefitting from its in-plane structural anisotropy. These results provide a pathway for the discovery and fabrication of 2D UWBS anisotropic materials, which become promising candidates for future solar-blind ultraviolet and polarization-sensitive sensors.

Recent Progress on Two-Dimensional Materials

“…Furthermore, Wei et al reported a new 2D material (GaPS4) with an ultralarge bandgap of 4.5 eV at monolayer condition in Fig. 28c, showing high responsivity (4.89 A•W −1 ), high detectivity (1.98 × 10 12 Jones), and high quantum efficiency (2390%) in the solar-blind ultraviolet region 823 . There are more and more 2D materials with wide bandgaps are discovered recently [824][825][826][827] , which is meaningful for the missile tracking and national security.…”

2D Ultrawide Bandgap Semiconductors: Odyssey and Challenges

“…In addition, As shown in Figure 10c, the GaPS 4 -based photodetector displays polarization-sensitive photoresponse with a linear dichroic ration up to 1.85 under 254 nm irradiation. [36] These results pave the way exploring new 2D UWBG anisotropic semiconductor materials, which become are becoming ideal choices for future solar-blind polarizationsensitive photodetectors. 2D ultrawide bandgap Dion-Jacobson layered perovskite oxides could serve in prospective optoelectronic devices owing to their unique structure, physical properties, and reduced dimension.…”

“…[50,[129][130][131] Wei's group reported an electrical anisotropy in GaPS 4 -based transistor through the angle-resolved electrical transport measurements. [36] GaPS 4 can be used as a promising candidate for future optoelectronic applications in solar-blind polarization-sensitive detection owing to the intrinsic ultrawide bandgap and interesting in-plane anisotropy. Recently, the transport properties of 2D h-TiO 2 -based field-effect transistor exhibits the switching performance of a typical device with the gate voltage in the range of −1 to 0.5 V at a fixed drain-source voltage (V ds ).…”

Research progress of IV–VI low-dimensional semiconductor materials and devices

“…Copyright 2020, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). [57] ；(b)SnSe2(1-x)S2x 合金场效应管在不同条件下 的输出曲线 [57] ；(c)准一维 Sn II Sn IV S3 纳米线的原子结构示意图 [107] ；(d)在平行模式下的角 分辨拉曼图谱 [107] ；(e)在垂直模式下的角分辨拉曼图谱 [107] ；(f)器件在不同波长激光照射下 的响应度 [107] ；(g)器件在不同波长激光照射下输出的光电流值与入射光角度的依赖关系的极 坐标图 [107] ；(h)Ga 元素与 P 元素取代 Ge 元素的取代示意图 [108] ；(i)GaPS4 的原子结构示意 图 [108] ；(j)在不同激光照射下器件的输出曲线 [108] ；(k)响应度、探测率及外量子效率随入射 光功率的变化曲线 [108] ；(l)在 254 nm 激光照射下，器件的光电流值与入射光角度的依赖关系 的极坐标图 [108] . Figure 9 (a) HRTEM images of SnSe2(1-x)S2x alloy (reproduced with permission [57] , Copyright 2012, Royal Society of Chemistry); (b) output curves of SnSe2(1-x)S2x alloy field effect tubes under different conditions (reproduced with permission [57] , Copyright 2012, Royal Society of Chemistry); (c) schematic diagram of atomic structure of quasi-one-dimensional Sn II Sn IV S3 nanowires (reproduced with permission [107] , Copyright 2019, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (d) angleresolved Raman atlas in parallel mode (reproduced with permission [107] , Copyright 2019, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (e) angle-resolved Raman atlas in vertical mode (reproduced with permission [107] , Copyright 2019, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (f) the responsiveness of the device under laser irradiation of different wavelengths (reproduced with permission [107] , Copyright 2019, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (g) polar coordinate diagram of the dependence between the photocurrent output value of the device under laser irradiation of different wavelengths and the angle of incident light (reproduced with permission [107] ,…”

“…Copyright 2019, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (h) schematic diagram of substitution of Ga element and P element for Ge element (reproduced with permission [108] , Copyright 2021, WILEY-VCH Verlag GmbH); (i) Schematic diagram of atomic structure of GAPS4 (reproduced with permission [108] , Copyright 2021, WILEY-VCH Verlag GmbH); (j) the output curve of the device under different laser irradiation (reproduced with permission [108] , Copyright 2021, WILEY-VCH Verlag GmbH); (k) curves of responsiveness, detection rate and external quantum efficiency changing with incident light power (reproduced with permission [108] , Copyright 2021, WILEY-VCH Verlag GmbH); (l) polar coordinate diagram of the dependence between the photocurrent value of the device and the angle of the incident light under the irradiation of 254 nm laser (reproduced with permission [108] , Copyright 2021, WILEY-VCH Verlag GmbH). [87] ，成功得到了垂直堆叠结构的异质结，其 SEM 图像如图 10(a)所示.对该异质结进行 表征分析，由于其具有高的晶格失配度，发现该异质结展现出了明显周期性的莫尔超晶格图案.…”