J. James, Hiromi Fujita, P. Carrington, Andrew R. J. Marshall, Susan Krier, A. Krier
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引用次数: 0
摘要
本文介绍了一种利用室温外部量子效率测量结果推导 GaSb/GaAs 自组装量子点器件中低于带隙吸收的方法。研究了在砷化镓太阳能电池的本征区、n 区和 p 区放置五层三角掺杂量子点的器件。在分析量子点的吸收强度和过渡态时,结合扩展的乌尔巴赫尾吸收的重要性得到了证明。计算得出量子点基态的理论综合吸收率为 1.04 × 1015 cm-1s-1,这与实验得出的数值 8.1 × 1015 cm-1s-1 非常吻合。从尾部吸收中分离出了润湿层和量子点的吸收贡献,并计算出了它们的过渡能量。利用这些转换能量和 1.42 eV 的砷化镓能隙,估算出量子点(320 meV)和润湿层(120 meV)的重空穴禁锢能量。
Characterization of Below-Bandgap Absorption in Type II GaSb Quantum Dots in GaAs Solar Cells
An approach to derive the below-bandgap absorption in GaSb/GaAs self-assembled quantum dot devices using room-temperature external quantum efficiency measurement results is presented. Devices with five layers of delta-doped quantum dots placed in the intrinsic, n- and p-regions of a GaAs solar cell are studied. The importance of incorporating an extended Urbach tail absorption in analyzing the absorption strength of quantum dots and the transition states is demonstrated. The theoretically integrated absorbance via quantum dot ground states is calculated as 1.04 × 1015 cm−1s−1, which is in reasonable agreement with the experimentally derived value 8.1 × 1015 cm−1s−1. The wetting layer and quantum dot absorption contributions are separated from the tail absorption and their transition energies are calculated. Using these transition energies and the GaAs energy gap of 1.42 eV, the heavy hole confinement energies for the quantum dots (320 meV) and for the wetting layer (120 meV) are estimated.