单片集成紫外-红外双波段雪崩探测器工作机理研究

High-performance dual-band, and even multi-band detection represent the development trend of the future detection technology. For application scenarios with weak target radiation and strong background interference, detectors hope to be equipped with multi-band detection capability and gain characteristics to improve the detection reliability and response sensitivity, respectively. This project put forward an ultraviolet/infrared dual-band avalanche photodiode with separate absorption and multiplication regions based on III-nitride superlattice absorption region, in which ultraviolet photons and infrared photons are absorbed through interband transition and intersubband transition, respectively, within superlattice structure. Both the two transition mechanisms induced photo-generated carriers are capable of transporting to multiplication region, where impact ionization happen, and finally to achieve dual-band detection with gain mode. Based on the key scientific issues such as refined design of band-structure and carrier dynamics within the above innovative dual-band avalanche photodiode, we will make a deep research into the underlying physics of carrier transition, impact ionization, identification transport and collection of photo-generated carriers from different transition mechanisms, and further carry out some experimental demonstration studies for prototype device. The development of the novel detectors will provide new ideas and new methods for developing monolithically integrated ultraviolet/infrared dual-band photodiodes with high performance.

高性能的双波段、甚至多波段探测技术是未来探测技术发展的主要方向。针对目标辐射微弱、背景干扰强的应用场景，一方面希望探测器能同时探测多个波段的信息来提高探测可靠性，另一方面希望其能工作于增益模式提高响应灵敏度。本项目提出一种基于氮化物超晶格吸收区的吸收倍增分离式紫外-红外双波段雪崩探测器件，紫外光子的吸收通过超晶格带间跃迁实现，红外光子的吸收通过超晶格子带能级间跃迁实现，两种跃迁机制产生的光生载流子在特定电压作用下均可迁移到雪崩区中发生碰撞离化从而实现双波段的增益模式探测。项目以该新型双波段雪崩探测器件的精细能带结构设计和载流子动力学行为等关键科学问题为引导，侧重于载流子的跃迁机制、碰撞离化特性、以及不同跃迁机制来源光生载流子的甄别输运和收集的基础物理研究，并开展原型器件实验论证工作。该新型器件的研制将为发展高性能的单片集成紫外-红外双波段探测器件提供新思路和新方法。

高性能的双波段、甚至多波段探测技术非常适用于目标辐射微弱、背景干扰强的应用场景，是未来探测技术发展的主要方向。本项目在氮化物吸收倍增分离式雪崩探测器的基础上，提出采用氮化物超晶格结构作为吸收区，分别利用带间跃迁和子带能级跃迁实现对紫外光子和红外光子的吸收，产生的光生载流子再迁移到雪崩区中实现增益探测。项目执行中首先理论分析了材料结构参数对器件能带结构、载流子浓度分布、极化效应、载流子跃迁等方面的影响。在微观层级进一步利用蒙特卡洛方法对载流子的输运进行跟踪和统计，得到载流子在不同结构中的碰撞离化特性。完整材料结构是采用分子束外延技术在蓝宝石衬底的AlN模板上生长，透射电镜表征表明材料晶体质量优良，GaN/AlN超晶格具有陡峭异质结界面。器件制作中开发了针对GaN/AlN复合材料体系的低损伤台面制作工艺和高透光率的P型欧姆接触工艺。制作完成的器件利用侧面45°入射的方式观测到与设计波段匹配的通信波段（~1.5µm）光电流响应和垂直入射的紫外波段（低于360 nm）光电流响应，实现超晶格结构器件线性增益超过500。项目取得的研究成果为发展实用化的高性能双波段探测器提供技术积累，器件未来将有望应用于复杂环境下的导弹预警、气候预测、深空探测等。