Bipolar two-dimensional avalanche photodetector
The bipolar two-dimensional avalanche photodetector (APD photodetector) achieves ultra-low noise and high sensitivity detection
High-sensitivity detection of few photons or even single photons has important application prospects in fields such as weak light imaging, remote sensing and telemetry, and quantum communication. Among them, the avalanche photodetector (APD) has become an important direction in the field of optoelectronic device research due to its characteristics of small size, high efficiency and easy integration. The signal-to-noise ratio (SNR) is an important indicator of APD photodetector, which requires high gain and low dark current. The research on van der Waals heterojunctions of two-dimensional (2D) materials shows broad prospects in the development of high-performance APDs. Researchers from China selected bipolar two-dimensional semiconductor material WSe₂ as the photosensitive material and meticulously prepared APD photodetector with a Pt/WSe₂/Ni structure that has the best matching work function, in order to solve the inherent gain noise problem of traditional APD photodetector.
The research team proposed an avalanche photodetector based on the Pt/WSe₂/Ni structure, which achieved highly sensitive detection of extremely weak light signals at the fW level at room temperature. They selected the two-dimensional semiconductor material WSe₂, which has excellent electrical properties, and combined Pt and Ni electrode materials to successfully develop a new type of avalanche photodetector. By precisely optimizing the work function matching among Pt, WSe₂ and Ni, a transport mechanism was designed that can effectively block dark carriers while selectively allowing photogenerated carriers to pass through. This mechanism significantly reduces the excessive noise caused by carrier impact ionization, enabling the photodetector to achieve highly sensitive optical signal detection at an extremely low noise level.
Then, in order to clarify the mechanism behind the avalanche effect induced by the weak electric field, the researchers initially evaluated the compatibility of the inherent work functions of various metals with WSe₂. A series of metal-semiconductor-metal (MSM) devices with different metal electrodes were fabricated and relevant tests were conducted on them. In addition, by reducing carrier scattering before the avalanche begins, the randomness of impact ionization can be mitigated, thereby reducing noise. Therefore, relevant tests were conducted. To further demonstrate the superiority of Pt/WSe₂/Ni APD in terms of time response characteristics, researchers further evaluated the -3 dB bandwidth of the device under different photoelectric gain values.
The experimental results show that the Pt/WSe₂/Ni detector exhibits an extremely low noise equivalent power (NEP) at room temperature, which is only 8.07 fW/√Hz. This means that the detector can identify extremely weak optical signals. In addition, this device can operate stably at a modulation frequency of 20 kHz with a high gain of 5×10⁵, successfully solving the technical bottleneck of traditional photovoltaic detectors that are difficult to balance high gain and bandwidth. This feature is expected to provide it with significant advantages in applications that require high gain and low noise.
This research demonstrates the crucial role of material engineering and interface optimization in enhancing the performance of photodetectors. Through ingenious design of electrodes and two-dimensional materials, a shielding effect of dark carriers has been achieved, significantly reducing noise interference and further improving detection efficiency.
The performance of this detector is not only reflected in the photoelectric characteristics, but also has broad application prospects. With its effective blocking of dark current at room temperature and efficient absorption of photogenerated carriers, this detector is particularly suitable for detecting weak light signals in fields such as environmental monitoring, astronomical observation, and optical communication. This research achievement not only provides new ideas for the development of low-dimensional material photodetectors, but also offers new references for the future research and development of high-performance and low-power optoelectronic devices.
Post time: Jun-18-2025