基于MoS2/Si异质结的雪崩光电二极管
Avalanche photodiodes based on MoS2/Si heterojunctions
摘要：
雪崩光电二极管（APD）是光电倍增管的半导体模拟物，提供非常高的内部电流增益和快速响应。APD在通信1、激光测距2、生物成像3和医学成像4中的广泛应用是令人感兴趣的，在这些应用中，APD提供优于经典的基于pn结的光电探测器的速度和灵敏度。APD的工作原理是基于通过反向偏置pn结中的碰撞电离的光电流倍增。APD可以在比例模式下操作，其中偏置电压低于击穿，或者在盖革模式下操作，其中偏置电压高于击穿。在比例模式下，倍增增益是有限的，从而允许光子能量鉴别，而在盖革操作模式下，倍增增益几乎是无限的，并且可以触发自持雪崩，从而允许检测单个光子5。在这里，我们展示了基于垂直堆叠单层MoS 2和p-Si的APD，形成突变的p-n异质结。利用该器件，我们证明了载波倍增超过1000。尽管APD中的这种倍增因子通常伴随着高噪声，但我们的器件显示出与常规光电二极管相当的极低噪声水平。这些异质结构允许实现简单和廉价的高性能和低噪声的光子计数器的基础上过渡金属二硫属化物。
英文摘要：
Avalanche photodiodes (APDs) are the semiconducting analogue of photomultiplier tubes offering very high internal current gain and fast response. APDs are interesting for a wide range of applications in communications1, laser ranging2, biological imaging3, and medical imaging4 where they offer speed and sensitivity superior to those of classical p-n junction-based photodetectors. The APD principle of operation is based on photocurrent multiplication through impact ionization in reverse-biased p-n junctions. APDs can either operate in proportional mode, where the bias voltage is below breakdown, or in Geiger mode, where the bias voltage is above breakdown. In proportional mode, the multiplication gain is finite, thus allowing for photon energy discrimination, while in Geiger mode of operation the multiplication gain is virtually infinite and a self-sustaining avalanche may be triggered, thus allowing detection of single photons5. Here, we demonstrate APDs based on vertically stacked monolayer MoS2 and p-Si, forming an abrupt p-n heterojunction. With this device, we demonstrate carrier multiplication exceeding 1000. Even though such multiplication factors in APDs are commonly accompanied by high noise, our devices show extremely low noise levels comparable with those in regular photodiodes. These heterostructures allow the realization of simple and inexpensive high-performance and low-noise photon counters based on transition metal dichalcogenides.
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