Large‐Scale Ultrathin 2D Wide‐Bandgap BiOBr Nanoflakes for Gate‐Controlled Deep‐Ultraviolet Phototransistors

Abstract

Ternary two‐dimensional (2D) semiconductors with controllable wide bandgap, high ultraviolet (UV) absorption coefficient, and critical tuning freedom degree of stoichiometry variation have a great application prospect for UV detection. However, as‐reported ternary 2D semiconductors often possess a bandgap below 3.0 eV, which must be further enlarged to achieve comprehensively improved UV, especially deep‐UV (DUV), detection capacity. Herein, sub‐one‐unit‐cell 2D monolayer BiOBr nanoflakes (≈0.57 nm) with a large size of 70 µm are synthesized for high‐performance DUV detection due to the large bandgap of 3.69 eV. Phototransistors based on the 2D ultrathin BiOBr nanoflakes deliver remarkable DUV detection performance including ultrahigh photoresponsivity (Rλ, 12739.13 A W−1), ultrahigh external quantum efficiency (EQE, 6.46 × 106%), and excellent detectivity (D*, 8.37 × 1012 Jones) at 245 nm with a gate voltage (Vg) of 35 V attributed to the photogating effects. The ultrafast response (τrise = 102 µs) can be achieved by utilizing photoconduction effects at Vg of −40 V. The combination of photocurrent generation mechanisms for BiOBr‐based phototransistors controlled by Vg can pave a way for designing novel 2D optoelectronic materials to achieve optimal device performance.

Van der Waals Epitaxial Growth of Mosaic‐Like 2D Platinum Ditelluride Layers for Room‐Temperature Mid‐Infrared Photodetection up to 10.6 µm

“…Figure 4f depicts the normalized photoresponse as a function of the pulsed light frequency, with ≈50 kHz for a 3 dB frequency ( f 3dB : frequency response dropped to 0.707 of its peak value), [ 42 ] which is among the fastest for 2D TMD‐based photodetectors. [ 28,31,43,44 ]…”

“…Figure 4f depicts the normalized photoresponse as a function of the pulsed light frequency, with ≈50 kHz for a 3 dB frequency (f 3dB : frequency response dropped to 0.707 of its peak value), [42] which is among the fastest for 2D TMD-based photodetectors. [28,31,43,44] To gain more insight into the operation mechanism, the energy band diagram of the PtTe 2 /Si vertical Schottky junction is illustrated in Figure 5a. Due to the different W F of multilayer PtTe 2 (≈4.80 eV) with n-Si (≈4.25 eV), when the mosaic-like 2D PtTe 2 layer is in contact with Si, a built-in potential will be formed.…”

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

“…[ 25 ] Although some studies have shown that the 2D‐hBN‐based deep‐UV detector presents a high on/off ratio of 10 3 , the missing wave range (only less than 210 nm detectable) and low responsivity make it difficult for practical SBPD application. [ 26–30 ] Up to date, several 2D WBSs, such as GaS, [ 31,32 ] Ga 2 In 4 S 9 , [ 33 ] NiPS 3 , [ 34 ] FePS 3 , [ 35 ] and BiOBr, [ 36 ] own intrinsic large bandgap (up to 3.4 eV) showing poor wavelength selectivity in solar‐blind photodetection. Compared with these 2D WBSs, 2D ultrawide bandgap semiconductors (UWBSs), as the next generation of semiconductor materials with bandgaps significantly wider than the 3.4 eV, [ 5 ] are particularly suitable for solar‐blind photodetection.…”

Recent Advances in 2D Rare Earth Materials

“…[ 14–21 ] The promising properties of 2D materials include attractive carrier mobility, peculiar excitonic, widely adjustable bandgaps, and light–matter interaction properties. [ 22–27 ] 2D materials have been proposed to be a potential material family for the next‐generation optoelectronic devices such as photodetector (PD), transistors, wearable devices, and ultracompact spintronics drives. [ 28–33 ] Nevertheless, the exploring of novel 2D materials is still important for broadening their applications.…”

“…[14][15][16][17][18][19][20][21] The promising properties of 2D materials include attractive carrier mobility, peculiar excitonic, widely adjustable bandgaps, and light-matter interaction properties. [22][23][24][25][26][27] 2D materials have been proposed to be a potential material family for the next-generation optoelectronic devices such as…”