基于梯度带隙MgZnO的单载流子倍增型深紫外探测器的研究

半导体深紫外探测器在紫外制导、保密通讯和火灾预警等领域具有广泛应用。单一载流子倍增过程是弱光探测高保真自放大的有效途径，但同时也对材料载流子碰撞离化的调控提出了更高要求。最新的研究结果表明，MgZnO具有较低的价带顶，在合金化的过程中，导带低与价带顶的移动量存在较大差别。这使得MgZnO材料中存在由于组分梯度所引起的导带空间梯度，即电子型准电场。与此同时，高增益、低噪声MgZnO基深紫外探测器的研究也一直是研究的难点。结合以上分析，本项目提出利用梯度带隙MgZnO/p-Si构成异质结，并通过调节Mg、Zn的组分梯度，获得存在准电场的载流子倍增层，以此实现对光生电子的单一倍增，这对提高增益和降低碰撞离化噪声水平是极为有利的。本项目将优化梯度带隙MgZnO的组分梯度及结构，研究梯度带隙材料中准电场对载流子碰撞离化的影响机制，最终实现基于梯度带隙MgZnO的单载流子倍增型深紫外探测器。

Deep Ultraviolet (DUV) photodetectors based on wide bandgap semiconductors have attracted much attention in recent years for their potential applications, including flame sensing, UV photography, chemical/biological agent detection, free space communications, missile plume sensing, and UV-astronomy, etc. On-type carrier multiplication is one of effective way of enhancing gain with low noise level. Among the latest findings are that MgZnO alloys have a larger ratio of conduction-band offset to valence-band offset. This indicates that quasi-electric forces for electrons in graded-band-gap MgZnO become much more marked than for holes. From other hand, to date, however, most of the DUV photodetectors based on MgZnO have low-performance, especially in responsivity, which is one of the important figures of merit for DUV detectors to be commercially applied. Motivated by the above reasons, in this application, via constructing heterojunctions based on Graded-Band-Gap-MgZnO/p-Si, we demonstrate a DUV photodetector with enhanced and tunable gain. The photodetector show sensitive spectral response, high quantum efficiency, and fast response time. The gain mechanism of the device is discussing in detail. In addition, this kind of structure may provide a new approach for high performance photodetector based on wide band gap semiconductor alloys.