A Si-based solar cell with Si-equivalent photovoltage and near-infrared absorbing characteristics using a shallow quantum well potential

利用先进的外延技术和带隙工程技术，采用带隙较小的多量子阱材料作为吸收层，开发了一种新型的外延硅基光伏电池及其相关技术。Si晶格匹配的SiGe合金基窄隙QW的使用允许在长于1 μ m的波长范围内的吸收，这很难被传统的Si基太阳能电池覆盖（即，吸收边降低）而不牺牲与Si的光电压相当的高光电压。通过标准吸收、光电导和光电压测量来确认吸收边降低，这指示太阳能电池操作。的QW的吸收边发生在较长的波长比的控制Si样品，显示出特征的3/2幂律依赖作为能量的函数，这是一致的空穴（2-D）和电子（3-D）的维数。载流子的热激发 关于我们 势垒带边的浅量子阱被证实为短路电流随温度的增加呈指数增加。QW吸收发生在能量小于Si带隙的情况下，并且获得了与Si太阳能电池相当的光电压（<approximately equal>0.4 - 0.6V）。结果发现，量子阱的位置起着重要的作用，有效的载流子阻塞的效率，由于量子阱的潜力。事实上，观察到由于载流子再分布引起的异常，即，纵向电场下量子阱阻挡剂的时间分辨发光中的动态背散射。结果表明，量子阱光伏电池中的载流子分布是可控的，通过调整使用故意掺杂的内置电场。内置的潜在的作用分别研究了光电流测量上的量子阱与集成SiGe渐变缓冲。为了提高太阳电池的性能，利用Si/SiO2技术实现了绝缘体上硅量子阱（SOI QW）。由于集成的反射镜特性，预期SOI几何形状允许吸收的增强，并且因此允许更高效的太阳能电池。量子阱的自发辐射和垂直入射反射显示出法布里-珀罗干涉条纹，这表明使用量子阱和501的光学腔。因此，吸收特性示出了谐振行为和波长选择性，用于作为谐振光电检测器的预期用途。少

An attempt is made to develop a new class of epitaxial Si-based photovoltaic cells and relevant technologies by using multiple quantum well (QW) of a smaller bandgap material as an absorbing layer with the aid of advanced epitaxial techniques and band-gap engineering. The use of Si-lattice-matched, SiGe-alloy-based narrow-gap QWs allows absorption in the wavelength regime longer than 1 mum that is hardly covered by conventional Si-based solar cells (i.e., absorption edge lowering) without sacrificing a high photovoltage equivalent to that of Si.The absorption edge lowering was confirmed by means of standard absorption, photoconductivity and photovoltage measurements, which indicates solar cell operation. The absorption edge of the QW occurred at longer wavelengths than that of a control Si sample, showing a characteristic 3/2 power-law dependence as a function of energy which is consistent with the dimensionality of holes (2-D) and electrons (3-D). Thermal excitation of carriers from t … More he shallow QW to the barrier band edge was confirmed as an exponential increase of shortcircuit current with increasing temperature. QW absorption occurred at energies smaller than the Si bandgap and a photovoltage comparable to that of a Si solar cell (<approximately equal>O.4-O.6V) was obtCarrier transport characteristics were studied in view of achieving a highly efficient photovolliaic effects. It was found that the location of QWs plays an important role in the efficiency of effective carrier blocking due to a QW potential. In fact, anomalies due to carrier redistribution were observed, i.e., dynamical backscattering, in the time-resolved luminescence of a QW blocker under longitudinal electric fields. The results indicates that carrier profiles in a QW photovoltaic cell are controllable by tuning the built-in electric field using intentional doping. The role of a built-in potential was separately studied by photocurrent measurements on a QW with an integrated SiGe-graded buffer. It was found that the photocurrent polarity switches abruptly as the wavelength is scanned in the near-infrared regime above the QW band-gap.To enhance the solar cell capability, the Si/S i02 technique exploited for the realization of a Si-on-insulator QW (SOI-QW). The SOI geometry is expected to allow an enhancement of absorption due to the integrated mirror characteristics and therefore a more efficient solar cell. Spontaneous emission from the QW and normal incidence reflectance showed Fabry-Perot interference fringes, which indicates an optical cavity using QW and 501. Accordingly, absorption characteristics show resonant behavior and wavelength selectivity for prospective use as resonant photodetector. Less