减小电极间距对少层GaSe光电探测器光响应的增强
Strong enhancement of photoresponsivity with shrinking the electrodes spacing in few layer GaSe photodetectors
摘要：
光电子学集成的一个关键挑战是光电探测器在纳米尺度上的灵敏度相对较差。通常认为，需要光电探测器中的大电极间距来吸收足够的光以保持高的光响应度并降低暗电流。然而，这将限制光电集成密度。通过空间分辨光电流研究发现，基于层状GaSe的金属-半导体-金属（MSM）光电探测器中的光电流主要来自金属-GaSe界面附近的光激发载流子，光电流有源区总是靠近电势较高的肖特基势垒。在直接隧穿发生之前，光响应率随着间距的减小而单调增加，在偏压为8 V，波长为410 nm时，底部接触器件的光响应率显著提高，最高可达5,000 AW-1。这比之前报告的结果提高了1，700倍以上。除了系统的实验研究的光响应度的依赖关系的底部和顶部接触MSM光电探测器的间距，理论模型也已经开发，很好地解释了这两种类型的设备配置的光响应度。我们的研究结果实现了缩小间距的同时，提高性能的二维半导体基MSM光电探测器，这可能为未来的高密度集成的二维半导体光电子器件的高性能铺平了道路。
英文摘要：
A critical challenge for the integration of the optoelectronics is that photodetectors have relatively poor sensitivities at the nanometer scale. It is generally believed that a large electrodes spacing in photodetectors is required to absorb sufficient light to maintain high photoresponsivity and reduce the dark current. However, this will limit the optoelectronic integration density. Through spatially resolved photocurrent investigation, we find that the photocurrent in metal-semiconductor-metal (MSM) photodetectors based on layered GaSe is mainly generated from the photoexcited carriers close to the metal-GaSe interface and the photocurrent active region is always close to the Schottky barrier with higher electrical potential. The photoresponsivity monotonically increases with shrinking the spacing distance before the direct tunneling happen, which was significantly enhanced up to 5,000 AW-1 for the bottom contacted device at bias voltage 8 V and wavelength of 410 nm. It is more than 1,700-fold improvement over the previously reported results. Besides the systematically experimental investigation of the dependence of the photoresponsivity on the spacing distance for both the bottom and top contacted MSM photodetectors, a theoretical model has also been developed to well explain the photoresponsivity for these two types of device configurations. Our findings realize shrinking the spacing distance and improving the performance of 2D semiconductor based MSM photodetectors simultaneously, which could pave the way for future high density integration of 2D semiconductor optoelectronics with high performances.
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