光伏半导体器件对能量小于禁带宽度光子的响应机理研究

利用光子能量为0.12 eV的10.6 μm连续激光分别辐照了禁带宽度为0.91和0.33 eV的光伏碲镉汞探测器. 实验表明,激光辐照下禁带宽度为0.91 eV的探测器输出正电压,而禁带宽度为0.33 eV的探测器对激光的响应方向却与之相反. 为了研究此现象,利用功率密度一定的10.6 μm激光辐照不同开路电压状态下禁带宽度为0.91 eV的探测器,实验结果证实初始开路电压是产生输出电压反向现象的原因. 对这一机理进一步分析发现,光伏探测器在光子能量小于禁带宽度的激光辐照下,其开路电压是热激发载流子导致的热生电动势和自由载流子吸收导致的晶格热效应共同决定的. 关键词： 能量小于禁带宽度的光子 光伏碲镉汞探测器 热生电动势 晶格热效应

Investigation of the response mechanism of photovoltaic semiconductor with sub-bandgap photons

The photovoltaic HgCdTe detectors with band gaps 0.91 and 0.33 eV are irradiated by 10.6 μm laser (0.12 eV photon energy), separately. It is found that output voltage of detector (0.91 eV band gap) is positive, while the response voltage of detector (0.33 eV band gap) is opposite to it. To investigate this phenomenon, the detector with a band gap of 0.91 eV is irradiated by a given power 10.6 μm laser under different initial open-circuit voltags. It is experimentally demonstrated that the phenomenon is caused by the initial open-circuit voltage. With further investigation, the open-circuit voltage of the photovoltaic detector is determined by both the thermovoltage caused by thermoexcited carrier and the crystal thermal effect produced by free carrier absorption under sub-bandgap laser irradiation.