SGER: New Approach to Revolutionize a Photovoltaic Detector Performance Using Electron Injection-Induced Effects in AlGaN

宽带隙GaN基半导体材料由于其在现代电子学中的重要地位而受到越来越多的关注。GaN的应用除了要获得高质量的材料外，还需要对其基本电学性质进行可控的修改。GaN基光伏探测器的光谱响应一般受到高能下较大的吸收系数和较小的少子扩散长度的限制。为了克服这些限制，最近的设计变化包括使用p-i-n而不是p-n结[1-4]，用AlxGa1-xN[1-3]或半透明凹进窗[2]代替GaN，以及背照式探测器配置[3]。然而，对基本(Al)GaN特性的调节，以提高III-氮化物器件的性能，从来没有被直接考虑过。这一方案的创新之处在于通过调整(Al)GaN中的少数载流子扩散长度来显著提高光伏探测器的性能。扩散长度是影响探测器量子效率和光响应的重要参数。基本的概念是由PI.最近的发现[5-8]定义的，即通过在固态器件中施加外部电压--p-n结或肖特基势垒--而向p-(Al)GaN注入电子，从而增加了关键的少数载流子扩散长度和寿命。观察到其他材料性质的一致变化，包括发光和光谱光响应，并归因于深亚稳态镁受体相关中心的荷电[6]。这项研究的现实意义是长期的(天)、革命性的(高达一个数量级！)通过短时间(最多1500秒)电子注入实现的(Al)GaN基光伏探测器的性能增强。这是因为增加的扩散长度改善了少数载流子的收集，并消除了载流子在收集之前重新结合的“死区”。拟议的项目风险很高，因为必须确定p-(Al)GaN[5-8]中新的电子注入诱导效应是否在本质上是普遍的，并代表p型材料的基本性质，或者相反，它们是否取决于材料的质量、生长和工艺条件。如果这种影响确实是普遍的，那么这种新颖而简单的方法的开发将显示出很高的回报，该方法通过操纵材料的传输特性来革命性地改变光伏探测器的性能，这可能会与设计和技术改进结合使用。SGER应用的成功将导致这种方法在商业探测器中的实施，并将推动这项技术的前沿，用于扩散长度至关重要的其他双极器件(晶体管、晶闸管)[6]。它计划提交一个目标建议(与康宁)的基础上，该项目的成功。这项研究的更广泛影响将是更深入地了解GaN及其相关化合物中的电子传输，将研究与教育相结合，并与业界建立伙伴关系。

Wide band gap GaN-based semiconductors are attracting increasing attention due to their importance in modern electronics. The applications of GaN necessitate the controlled modification of its fundamental electronic properties, in addition to the availability of high quality material. The spectral response of the GaN-based photovoltaic detectors is generally limited by the large absorption coefficient at high energies and the small minority carrier diffusion length. Recent design changes, to overcome these limitations, include the use of p-i-n instead of p-n junction [1-4], substitution of GaN by AlxGa1-xN [1-3] or semitransparent recessed windows [2], and a back-illuminated detector configuration [3]. However, a tuning of fundamental (Al)GaN properties, to boost the performance of III-Nitride devices, was never directly considered. The innovation in this proposal is to significantly enhance a photovoltaic detector performance by tailoring the minority carrier diffusion length in (Al)GaN. The diffusion length is a crucial parameter for the detector quantum efficiency and photoresponse. The underlying concept is defined by the PI.s recent findings [5-8] that electron injection into p-(Al)GaN from the application of an external voltage in a solid state device--p-n junction or Schottky barrier-increases the critical minority carrier diffusion length and lifetime. Consistent changes were observed in other material properties, including luminescence and spectral photoresponse, and were attributed to charging of deep metastable Mg-acceptor-related centers [6]. The practical significance of this research is a long-term (days), revolutionary (up to an order of magnitude!) performance enhancement for (Al)GaN-based photovoltaic detectors, achieved through short time (at most 1500 sec) electron injection. This is because the increased diffusion length improves minority carrier collection and eliminates the "dead space", where carriers recombine before they are collected. The proposed project is of high risk, since it must be determined whether the novel electron injection-induced effects in p-(Al)GaN [5-8] are universal in nature and represent a fundamental property of the p-type material, or if instead they depend on the material's quality, growth, and processing conditions. If, indeed, the effects are universal, a high pay off will be manifested in a development of this novel and simple approach to revolutionize photovoltaic detector performance by manipulating the material.s transport properties, which will likely be used in combination with design and technology improvements. Success in this SGER application will lead to the implementation of this approach in commercial detectors, and will advance the frontiers of this technology for use in other bipolar devices for which the diffusion length is critical (transistors, thyristors) [6]. It is planned to submit a GOALI proposal (with Corning) based on success of this project. The broader impact of this research will be a dipper understanding of electron transport in GaN and related compounds, the integration of research with education, and partnership with industry.