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The two-dimensional (2D) Ruddlesden−Popper phase all-inorganic halide perovskite Cs2PbI2Cl2 has attracted tremendous attention because of its high carrier mobility, strong light-absorbing ability, and excellent environmental stability, possessing enormous potential for use as a high-performance optoelectronic device. Here, we present two transistor devices based on monolayer (ML) Cs2PbI2Cl2 and reveal their performance and current transport mechanisms through ab initio quantum transport calculations. The n-type 10 nm metal-oxide-semiconductor field-effect transistor shows a high on-state current Ion of 3160 μA/μm, and excellent performance regarding subthreshold swing, intrinsic delay time (τ), and power consumption, which completely match the International Roadmap for Device and Systems (2021 version) targets for high-performance devices and low-power devices in 2028. Moreover, phototransistors based on monolayer Cs2PbI2Cl2 also display a strong response to UV light, with a light-to-dark current ratio reaching a maximum of 104. Meanwhile, a high specific detectivity of 2.45 × 1011 Jones is obtained. The results of our study suggest that ML Cs2PbI2Cl2 is a promising candidate for high-performance transistors. [ABSTRACT FROM AUTHOR]

The all-inorganic perovskite CsPbCl3 has attracted significant attention for its excellent carrier mobility and high optical absorption coefficient, demonstrating great potential for use as a high-performance photodetector. However, the severe toxicity of lead and its narrow-band response in the UV region pose a huge challenge to the application of the perovskite. In this study, we reduce the toxicity of CsPbCl3 by substituting Mn atoms for Pb atoms and introduce a wide-bandgap semiconductor p-GaN to improve the photoresponse of CsPbCl3 in the UV region. Mn-doped CsPbCl3/GaN heterojunction is prepared by transferring the synthesized Mn-doped CsPbCl3 precursor solution onto p-GaN substrates via the spin-coating method. The morphology and optical properties of the heterojunction are characterized in various ways, and the current–voltage characteristics and optical response properties of the Mn-doped CsPbCl3/GaN heterojunction photodetector are also measured. The rectification behavior and UV–visible dual-band response of the heterojunction are demonstrated, with the response in the UV region extending to 320 nm. Furthermore, the calculations, which are based on density functional theory, confirm that the optical absorption of the Mn-doped CsPbCl3/GaN heterojunction is significantly enhanced compared with that of the isolated material. Meanwhile, a type-II energy band arrangement is found at the heterojunction interface. The results of this study suggest that Mn-doped CsPbCl3/GaN heterojunctions are potential candidates for use as UV–visible dual-band photodetectors. [ABSTRACT FROM AUTHOR]

An Al0.4Ga0.6N-based metal–semiconductor–metal (MSM) ultraviolet (UV) photodetector (PD) based on intentionally asymmetrical polarized Al0.55Ga0.45N/Al0.4Ga0.6N/Al0.65Ga0.35N heterostructure has been fabricated and investigated, which achieves the self-powered capabilities. Operated at zero bias, the device presents an ultralow dark current of 7.8 × 10−13 A, a high peak responsivity of 0.04 A/W at ∼275 nm, a cut-off wavelength at ∼285 nm, and a corresponding detectivity of 3.1 × 1012 Jones. In comparison, the device with symmetrical heterostructure has no response at 0 V, confirming the effect of the proposed asymmetrical MSM structure. Furthermore, it is expressly demonstrated that the structure provides an asymmetrical energy band due to different barrier heights at the metal/Al0.4Ga0.6N and metal/Al0.55Ga0.45N/Al0.4Ga0.6N Schottky contacts and enhances the built-in electric field in the Al0.4Ga0.6N active layer owing to its polarization effect through simulations theoretically. Therefore, the improvement of photogenerated carrier transport can be obtained at 0 V, contributing to the high-performance self-powered UV PD. [ABSTRACT FROM AUTHOR]

The high carrier mobility, appropriate band gap and good environmental stability of two-dimensional (2D) MoSi2N4 enable it to be an appropriate channel material for transistors with excellent performance. Therefore, we predict the performance of double-gate (DG) metal–oxide-semiconductor field-effect transistors (MOSFETs) based on monolayer (ML) MoSi2N4 by ab initio quantum-transport calculations. The results show that the on-state current of the p-type device is remarkable when the gate length is greater than 4 nm, which can meet the high performance requirements of the International Technology Roadmap for Semiconductors (ITRS), 2013 version. Moreover, the gate length can be reduced to 3 nm when an underlap (UL) structure is employed in the MOSFET, and the sub-threshold swing, intrinsic delay time and power consumption also perform well. The calculation results reveal that ML MoSi2N4 will be a promising alternative for transistor channel materials in the post-silicon era. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) MoS2 was grown on AlGaN(GaN) substrates by chemical vapor deposition (CVD) and 2D-3D MoS2-AlGaN(GaN) heterostructures were formed. The MoS2 crystal on AlGaN surface has a mixed and irregular shape including single and multiple layers, while the single layer of triangular MoS2 is basically prepared on GaN surface. Combined with theoretical first-principles analysis, it is found the adsorption of AlGaN to MoS2 is lower than that of GaN, which leads to the deposition of MoS2 molecules on AlGaN surface, forming multilayer shapes. In addition, Both the MoS2-AlGaN(GaN) heterostructures exhibit indirect band gaps and broad-band light absorption performances. [ABSTRACT FROM AUTHOR]

All-inorganic metal halide perovskites (MHPs) have attracted increasing attention because of their high thermal stability and band gap tunability. Among them, CsPbCl 3 is considered a promising semiconductor material for visible-ultraviolet dual-band photodetectors because of its excellent photoelectric properties and suitable band gap value. In this work, we fabricated a visible-ultraviolet dual-band photodetector based on a CsPbCl 3 /p-GaN heterojunction using the spin coating method. The formation of the heterojunction enables the device to exhibit obvious dual-band response behavior at positive and negative bias voltages. At the same time, the dark current of the device can be as low as 2.42 × 10 -9 A, and the corresponding detection rate can reach 5.82 × 10 10 Jones. In addition, through simulation calculations, it was found that the heterojunction has a type II energy band arrangement, and the heterojunction response band light absorption is significantly enhanced. The type II energy band arrangement will separate electron-hole pairs more effectively, which will help improve device performance. The successful implementation of visible-ultraviolet dual-band photodetectors based on a CsPbCl 3 /p-GaN heterojunction provides guidance for the application of all-inorganic MHPs in the field of multi-band photodetectors., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Two-dimensional (2D) organic-inorganic hybrid perovskites (OIPs) have exhibited ideal prospects for perovskite photodetectors (PDs) owing to their remarkable environmental stability, tunable band gap, and structural diversity. However, most perovskites face the great challenge of a narrow spectral response. Integrating 2D OIPs with a suitable wide band gap semiconductor gives opportunities to broaden the response spectra. Here, a photodetector based on the BA 2 PbI 4 /GaN heterostructure with a broadband photoresponse covering from the ultraviolet (UV) to visible band is designed. We demonstrate that the device is capable of detecting in the UV region by p-GaN being integrated with BA 2 PbI 4 . The morphology and material optical properties of BA 2 PbI 4 are characterized by transmission electron microscopy (TEM) and photoluminescence (PL). Additionally, the current-voltage ( I - V ) characteristics and photoresponses of the BA 2 PbI 4 /GaN heterojunction photodetector are investigated. The response spectrum of the photodetector is broadened from the visible to UV region, exhibiting good rectifying behavior in the dark conditions and a broadband photoresponse from the UV to the visible region. Additionally, the energy band is used to analyze the current mechanism of the BA 2 PbI 4 /GaN heterojunction PD. This study is expected to provide a new insight of optoelectronic devices by integrating 2D OIPs such as BA 2 PbI 4 and wide-band-gap semiconductors such as GaN to broaden the response spectra.