EAPSI:Investigation of Radiation Tolerance of Novel Semiconductor Materials for Space Power

光伏(PV)是一种能够用于空间探索的技术，在设计整个系统之前，需要很好地描述和理解所采用技术的生命周期。在中地球轨道(MEO)或轨道半径为地球半径(Re)1.8至2.5倍的轨道上运行的卫星的一个主要问题是穿过Van Allen带时产生的高能辐射效应，在Van Allen带中，电荷粒子被地球磁场捕获。由于光伏系统因暴露在辐射中而退化，卫星或飞船的总功耗受到光伏系统在寿命结束时所能提供的功率的限制。该项目的基本目标是了解和设计在高辐射通量下表现出更好电学特性的材料，这是空间光伏界非常感兴趣的话题。这项研究将在日本原子能机构的半导体分析和辐射影响小组完成，并由半导体材料辐射效应领域的专家佐藤信一郎博士协助完成。该设施拥有最先进的太阳能电池辐照和测试设施，可以在相对较短的时间内完成广泛的研究。在这个项目中，将生长三套应变平衡量子点/量子井太阳能电池(QDSC/QWSC)和量子点/量子井(QD/QW)测试结构。第一组将针对菌株中性条件。第二组将通过减薄间隙应变补偿层来设计为具有轻微压缩应变(通过x射线衍射仪验证为百万分之1000)。最后，第三组将具有更厚的间隙应变补偿层，导致轻微拉伸(~1000ppm)的量子点堆栈。所需位移敲击能量的变化应该可以通过DLT缺陷密度的变化来测量，如果QD堆栈保持较薄，残余应变的相对较小的变化应该不会对电学性能产生不利影响。由于量子点太阳能电池也将被包括在内，因此将有可能将这些变化与设备的电学特性的变化相关联。这一器件阵列使得有可能将残余应变的影响从固有的量子点属性中分离出来，以便更好地了解添加纳米结构对材料的辐射耐受性的影响。为了研究三维量子限制和一维量子限制对抑制太阳电池中辐射效应的影响，将用InGaAs/GaAsQW重复这一研究。该NSF EAPSI奖是与日本科学促进会合作资助的。

Photovoltaics (PV) is an enabling technology for space exploration, and the lifecycle of the technology employed needs to be well characterized and well understood before the full system can be designed. A major concern for the longevity of satellites in Medium Earth orbit (MEO), or orbital radii from 1.8 to 2.5 times the Earth's radius(Re) is the high energy radiation effects from passing through the Van Allen belts where charge particles are trapped by the Earth's magnetic field. Since the PV system degrades from exposure to radiation, the total power consumption of the satellite or vessel is limited by what the PV system can provide at end-of-life. The underlying goal of this project is to understand and engineer materials that exhibit better electrical characteristics under high radiation fluences, a topic of great interest to the space PV community. This research will be completed at the Semiconductor Analysis & Radiation Effects group of the Japan Atomic Energy Agency with the assistance of Dr. Shin-Ichiro Sato, an expert in the field of radiation effects in semiconductor materials. This facility possesses state-of-the-art solar cell irradiation and testing facilities, enabling completion of an extensive study in a relatively short period of time. For this project, three sets of strain balanced quantum dot/quantum well solar cells (QDSC/QWSC) and quantum dot/quantum well (QD/QW) test structures will be grown. The first set will target a strain-neutral condition. The second set will be designed to have a slightly compressive strain (~1000 parts per million (ppm) verified via x-ray diffractometry) by thinning the GaP strain compensation layer. Finally, the third set will have a thicker GaP strain compensation layer, resulting in a slightly tensile (~1000 ppm) strained QD stack. A change in required displacement knock-on energy should be measurable via changes in defect density from DLTS, and if the QD stack is kept thin, relatively minor changes in residual strain should not have detrimental effects on electrical properties. Since QD solar cells will also be included, it will be possible to correlate these changes to changes in electrical properties of devices. This array of devices makes it possible to deconvolve effects of residual strain from inherent QD properties in order to enhance understanding of the effects adding nanostructures has on radiation tolerance of the material. The study will be repeated with InGaAs/GaAs QWs in order to investigate the impact of 3D quantum confinement vs 1D quantum confinement on suppressing radiation effects in solar cells. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.