Carrier recombination dynamics in III-N photodetectors

紫外光探测器有许多用途，如化学和生物分析或火焰检测。在恶劣的辐射环境中，含能粒子的损伤会降低紫外光探测器的灵敏度。该项目将研究基于氮化镓(GaN)的光电探测器的恢复技术。这一目标将通过在外加电压下原位电荷注入来对GaN的基本性质、电子寿命和扩散长度进行电学调整来实现。光电探测器的灵敏度将完全恢复，并恢复到照射前的原始状态。该项目将促进对GaN基半导体和器件中点缺陷和扩展缺陷的本质的基本理解。该项目将整合研究生和本科生层面的研究和教育，并以活跃的行业合作伙伴为特色。技术：该项目重点是通过向基于氮化镓(GaN)的紫外光探测器注入电荷来电气缓解辐射诱导的缺陷。最终目标是生产抗辐射和高效的设备。该项目基于PI之前的发现，即电荷注入p型GaN导致材料的基本电子性质发生重大变化，特别是载流子寿命和扩散长度。这些变化导致光电探测器响应(量子效率)提高了一个数量级。因此，使用注入GaN p-i-n器件的固态正向偏置电荷的短脉冲来改善受辐射影响的光电探测器的性能是可能的。该项目将有助于更好地了解宽禁带半导体与高能粒子之间的相互作用，包括电子、伽马射线光子和质子，以及辐射引起的缺陷的性质。电荷注入将导致光电探测器顶部p型吸收层中少数电子的扩散长度增加，从而提高器件的量子效率，并“治愈”高能粒子的不利影响。PI实验室中独特的电学和光学研究相结合，将揭示导致兴趣效应的机制。少数载流子寿命和扩散长度的研究将在不同温度下使用超快时间分辨阴极发光和电子束感应电流进行独立的实验。多色连续波阴极发光将被用来评估辐照对GaN中穿线位错密度的影响。最后，该项目的最终目标是将电荷注入制度(电流、电压、持续时间)和照射剂量联系起来，从而控制光电探测器的性能并从纯电气方法的辐射损害中恢复。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Ultraviolet photodetectors have many uses, such as chemical and biological analysis or flame detection. Damage by energetic particles degrades the sensitivity of ultraviolet photodetectors in harsh radiation environments. This project will study techniques for recovery of photodetectors based on gallium nitride (GaN). This aim will be achieved by electrical tailoring of GaN fundamental properties, the electron lifetime and diffusion length, by in-situ charge injection under applied voltage. Photodetector sensitivity will recover completely and return to the original state prior to irradiation. The project will advance the fundamental understanding of the nature of point and extended defects in GaN-based semiconductors and devices. The project will integrate research and education at the graduate and undergraduate levels and features an active industrial partner.Technical: This project focuses on electrical mitigation of radiation-induced defects by charge injection into ultraviolet photodetectors based on gallium nitride (GaN). The ultimate aim is to produce radiation hard and efficient devices. The project hinges on the PI's previous findings that charge injection into p-type GaN leads to considerable changes in the material's fundamental electronic properties, particularly the carrier lifetime and diffusion length. These changes result in an order of magnitude enhancement of the photodetector response (quantum efficiency). It is therefore possible to improve performance of photodetectors, affected by radiation, using short pulses of solid-state forward-bias charge injection into GaN p-i-n devices. The project will lead to a better understanding of the interaction between wide band gap semiconductors and highly energetic particles, including electrons, gamma-ray photons and protons, as well as of the nature of radiation-induced defects. Charge injection will result in enhanced minority electron diffusion length in the top p-type absorption layer of a photodetector, thus increasing the quantum efficiency for the device and "healing" the adverse impact of highly energetic particles. A unique combination of electrical and optical studies in the PI’s lab will shed light on the mechanism, which is responsible for the effect of interest. Studies of minority carrier lifetime and diffusion length will be carried out in independent experiments using ultrafast time-resolved cathodoluminescence and electron beam-induced current at various temperatures. Polychromatic continuous-wave cathodoluminescence will be employed for assessment of irradiation impact on threading dislocation density in GaN. Finally, the ultimate goal of this project is to correlate charge injection regimes (current; voltage; duration) and irradiation doses, thus proceeding towards control of photodetector performance and recovery from radiation damage by purely electrical means.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.