Sensitive and Ultrabroadband Phototransistor Based on Two‐Dimensional Bi₂O₂Se Nanosheets

Abstract

Bi2O2Se, a high‐mobility and air‐stable 2D material, has attracted substantial attention for application in integrated logic electronics and optoelectronics. However, achieving an overall high performance over a wide spectral range for Bi2O2Se‐based devices remains a challenge. A broadband phototransistor with high photoresponsivity (R) is reported that comprises high‐quality large‐area (≈180 µm) Bi2O2Se nanosheets synthesized via a modified chemical vapor deposition method with a face‐down configuration. The device covers the ultraviolet (UV), visible (Vis), and near‐infrared (NIR) wavelength ranges (360–1800 nm) at room temperature, exhibiting a maximum R of 108 696 A W−1 at 360 nm. Upon illumination at 405 nm, the external quantum efficiency, R, and detectivity (D*) of the device reach up to 1.5 × 107%, 50055 A W−1, and 8.2 × 1012 Jones, respectively, which is attributable to a combination of the photogating, photovoltaic, and photothermal effects. The devices reach a −3 dB bandwidth of 5.4 kHz, accounting for a fast rise time (τrise) of 32 µs. The high sensitivity, fast response time, and environmental stability achieved simultaneously in these 2D Bi2O2Se phototransistors are promising for high‐quality UV and IR imaging applications.

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

“…The EQE was calculated to be 1.3 × 10 5 % under 245 nm light, which is the highest among those obtained under wavelengths of light from 245 to 450 nm. Such a high EQE reveals an obvious high gain ( G ) of the device illuminated under the UV light 38–42. If the quantum efficiency (η) is ignored, the G is the same meaning as EQE , which is often produced by the prolonged carrier lifetime attributed to the defects of 2D materials 39.…”

“…The value of θ decreases from 1.03 to 0.36 revealing the photoresponse mechanism changes from photoconduction effect to photogating effect by V g (Figure 6b). 38 Due to the enhancement of the photogating effect, the R λ value and EQE are increased up to 12 739.13 A W −1 (Figure 6c) and 6.46 × 10 6 % (Figure S8b, Supporting Information) with a high D * of 8.37 × 10 12 jones of at V g = 35 V. Moreover, the D * can be further increased from 10 12 to 10 14 Jones by controlling the V g (Figure S8c, Supporting Information). On the other hand, the photoconduction effect at V g of −40 V results in a fast photoresponse, as the −3 dB cut‐off frequency is increased from 735 Hz at 0 V to 3414 Hz at −40 V (Figure 6d), corresponding τ rise is decreased from 476 to 102 µs.…”

High‐Fidelity Transfer of 2D Bi2O2Se and Its Mechanical Properties

“…[1][2][3] Bismuth oxyselenide (Bi 2 O 2 Se), a semiconducting 2D material featured by narrow bandgap (≈0.8 eV), high electronic mobility (20 000 cm 2 V −1 s −1 at 2 K), and good air stability, shows great potential for applications in high-performance electronics, optoelectronics, and flexible devices. [4][5][6][7][8][9][10] For example, the photodetectors based on Bi 2 O 2 Se with ultrabroadband responses, [7] high on/off ratio, and ultrahigh photodetectivity [8] have been demonstrated. Bi 2 O 2 Se is also an important material to fabricate three-terminal memristors with high speed and low energy consumption for neuromorphic functions.…”

Novel two-dimensional monoelemental and ternary materials: growth, physics and application

“…Yin et al reported an infrared PD based on 2D Bi 2 O 2 Se, which demonstrated a high sensitivity of 65 A · W −1 at 1200 nm and ultrafast photoresponse of ~1 ps at room temperature ( Figure 6J) [171]. Through a modified CVD method, Tong et al synthesized large-area (≈180 μm) Bi 2 O 2 Se nanosheets and constructed PDs [54]. The photodetection wavelength of the device covers the UV-Vis-NIR range, and the R reaches 108,696 A · W −1 (at 360 nm), 50,055 A · W −1 (at 405 nm), 25,505 A · W −1 (at 532 nm), 843.5 A · W −1 (at 808 nm), 118 A · W −1 (at 1310 nm) and 22.12 A · W −1 (at 1550 nm).…”

“…Thus, it is indispensable to focus on these novel materials to accelerate the synthesis process and the development of magnetic and spintronic applications. Among them, air-stable Bi 2 O 2 Se nanosheets with an ultralow electron effective mass (0.14 m 0 ) and a narrow bandgap (~0.8 eV) have exhibited extraordinary electron mobility (28,900 cm 2 · V −1 · s −1 at 2 K) and high on/off ratio (10 6 ) [54]. In contrast, the layer-by-layer interaction is electrostatic force instead of vdWs.…”