Atomically Thin Gallium Nitride for High‐Performance Photodetection

Abstract

Gallium nitride (GaN) technology has matured and commercialised for optoelectronic devices in the ultraviolet (UV) spectrum over the last few decades. Simultaneously, atomically thin materials with unique features have emerged as contenders for device miniaturization. However, the lack of successful techniques to produce ultra‐thin GaN prevents access to these new predicted properties. Here, this important gap is addressed by printing millimeter‐large ultra‐thin GaN nanosheets (NS) (≈1.4 nm) using a simple two‐step process that simultaneously introduces nitrogen point defects. This extends the photoelectrical spectral response from UV (280 nm) to near infrared (NIR) (1080 nm). The GaN‐based photodetectors display excellent figures of merit, having a responsivity (2.72 × 104 A W−1) up to four orders of magnitude higher than the commercial photodetectors at room temperature, despite being 102–103 times thinner. The photodetectors exhibit fast switching, with rise and decay time in the range of microseconds. The state‐of‐the‐art device performance originates from the ultra‐thin nature of GaN NS coupled with nitrogen point vacancies in the synthesis process. This work presents the opportunity to significantly expand the reach of GaN semiconductor technology and may lead to applications in high‐performance miniaturized imaging systems, spectroscopy, communication, and integrated optoelectronic circuits.

Dual‐Mode Conversion of Photodetector and Neuromorphic Vision Sensor via Bias Voltage Regulation on a Single Device

“…As a result, most optoelectronic devices can only fulfill the role of a single photodetector or an NVS. [35][36][37][38][39] To address this, researchers have proposed utilizing threeterminal devices or altering the direction of voltage to control the photoresponse speed. [40][41][42][43][44] However, three-terminal devices that use gate voltage to regulate the photoresponse speed not only require more complex preparation processes, device structures, and operating procedures but also have significantly higher power consumption due to the additional gate volt-age applied.…”

“…As a result, most optoelectronic devices can only fulfill the role of a single photodetector or an NVS. [ 35–39 ]…”

Ultrahigh-Responsivity Ultraviolet Photodetectors Based on AlGaN/GaN Double-Channel High-Electron-Mobility Transistors

“…It can be calculated by the noise equivalent power (NEP): , D * = A × B NEP , where A is the active area, B is the electrical bandwidth. Generally, the NEP of the device can be estimated according to the equation: ,,, NEP = 2 q I D R , where q is the electronic charge constant and I D is the dark current density, and then the specific detectivity D * was calculated to be 4.36 × 10 16 Jones at 2 V. However, this specific detectivity value was overestimated because it only considered the short noise, but the noise of PDs commonly includes shot noise, thermal noise, and flicker (1/ f ) noise. , In order to more precisely measure specific detectivity, it is crucial to take into account the contribution of flicker noise at low frequency. Figure a shows the noise power spectra of PD measured in the frequency range of 1 to 100 kHz at various drain voltages.…”

“…Ultraviolet (UV) photodetectors (PDs) are widely employed in numerous applications, including missile warning, astronomical exploration, fire alarming, chemical and biological analysis, environmental monitoring, optical communications, etc. − Due to a direct bandgap of 3.4 eV and other excellent properties, GaN-based semiconductors are a great candidate for next-generation high-sensitivity UV detection. − …”