AlGaN基深紫外雪崩光电二极管的应力-位错-极化协同调控物理机制研究

The key problems for the development of the AlGaN-based deep ultraviolet avalanche photodiodes (APDs) are the growth of AlGaN materials with high Al component and the low p-type doping concentration. As a result, there is no significant breakthrough for the performance of AlGaN APDs until now. This project will focus on these two key issues, according to the physical properties of AlGaN materials and devices, we will design and fabricate the novel AlGaN heterostructures with graded Al content and separated absorption and multiplication AlGaN p-i-n-i-n APD structure by using strong polarization property of AlGaN heterostructures. The physical modes of stress-dislocation-polarization related to the devices’ performance would be established by investigating the relationship between stress and dislocation in AlGaN epitaxial materials, and influence of polarization field on the dark current and internal gain for AlGaN APDs. Finally, the coordinate control of materials and device structures would improve the performance of AlGaN APDs, and alleviate the difficulties of material growth and p-type doping for AlGaN APDs. This project could provide basic theoretical solutions for the realization of high-performance nitride deep ultraviolet APDs.

目前受到重点研究的AlGaN深紫外雪崩光电二极管由于存在高Al组分AlGaN材料生长困难和p型有效掺杂浓度低的难题，其器件性能提升一直未有重要突破。本项目将针对这两大关键问题，从AlGaN材料和器件的物理本质出发，利用III族氮化物半导体异质结的强极化特性，设计和制备新型渐变组分AlGaN异质结以及吸收区和倍增区分离的p-i-n-i-n雪崩光电二极管结构。通过研究AlGaN外延材料中应力和位错，以及器件异质结中极化场对于深紫外雪崩光电二极管暗电流和内部增益影响的物理机制，建立与器件性能相关联的应力-位错-极化协同调控物理关系模型，实现AlGaN雪崩光电二极管中材料和器件结构的综合调控，缓解器件对材料的高晶体质量和p型掺杂两大难题的依赖程度，为高性能的氮化物深紫外雪崩光电探测器的制备和实现提供基础性的理论解决方法。

目前受到重点研究的AlGaN深紫外雪崩光电二极管由于存在高Al组分AlGaN材料生长困难和p型有效掺杂浓度低的难题，其器件性能提升一直未有重要突破。本项目将针对这两大关键问题，从AlGaN材料和器件的物理本质出发，利用III族氮化物半导体异质结的强极化特性，设计和制备出新型渐变组分AlGaN异质结以及吸收区和倍增区分离的p-i-n-i-n雪崩光电二极管结构，并通过III族氮化物DBR结构的引入，有效改善了AlGaN深紫外雪崩光电二极管的光谱响应特性。通过研究AlGaN外延材料中应力和位错，以及器件异质结中极化场对于深紫外雪崩光电二极管暗电流和内部增益影响的物理机制，建立了材料物理参数协同调控器件性能的物理关系模型。在器件设计和仿真基础上，将具有极化掺杂的p-AlxGa1-xN/AlyGa1-yN异质结应用于p-i-n-i-n 雪崩光电二极管的倍增层，开展器件制备研究。项目探索了能够抑制AlGaN雪崩光电二极管器件边缘电场的特殊倾斜台面刻蚀工艺，有效防止器件边缘提前击穿；研究器件绝缘介质保护层的优化沉积方法和表面钝化工艺，有效降低器件漏电流并防止器件老化。结合器件电流-电压曲线测试，探究了高Al组分AlGaN深紫外雪崩光电二极管的物理输运机制。项目实现了AlGaN雪崩光电二极管中材料和器件结构的综合调控，缓解器件对材料的高晶体质量和p型掺杂两大难题的依赖程度，为高性能的氮化物深紫外雪崩光电探测器的制备和实现提供基础性的理论解决方法。