Similar to other high quality crystalline absorbers, an accurate knowledge of surface passivation of crystalline germanium (c-Ge) substrates is crucial for a straightforward improvement of photovoltaic device performance. For crystalline silicon devices, this information is typically obtained by quasi-steady-state photoconductance (QSS-PC) technique using Sinton WCT-120 tool. In this article, we explore the conditions to adapt this measurement technique to c-Ge substrates. Based on PC-1D simulations, we deduce that a minimum effective lifetime is needed corresponding to an effective diffusion length equal to the substrate thickness. Apart from this, an accurate estimation of the total photogeneration inside the c-Ge sample is also mandatory. This condition implies that the light intensity that impinges onto the sample must be measured with a c-Ge sensor, although the integrated c-Si sensor can be used for high flash intensities. Additionally, the optical factor used to evaluate sample reflectance must be also known, which is determined by measuring robust effective lifetime values under photoconductance decay conditions. Finally, knowledge about carrier mobility in c-Ge is also necessary to translate the measured photoconductance to the corresponding excess carrier density values. Lifetime measurements of passivated c-Ge substrates done by QSS-PC technique are validated by comparing them with the ones obtained by microwave photoconductance technique.

中文翻译：

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准稳态光电导技术在结晶锗基板寿命测量中的应用

与其他高质量晶体吸收器类似，准确了解晶体锗 (c-Ge) 衬底的表面钝化对于直接提高光伏器件性能至关重要。对于晶体硅器件，该信息通常通过使用 Sinton WCT-120 工具的准稳态光电导 (QSS-PC) 技术获得。在本文中，我们探讨了将这种测量技术应用于 c-Ge 衬底的条件。基于 PC-1D 模拟，我们推断出所需的最小有效寿命对应于等于基板厚度的有效扩散长度。除此之外，还必须准确估计 c-Ge 样品内的总光生。这种情况意味着入射到样品上的光强度必须用 c-Ge 传感器测量，尽管集成的 c-Si 传感器可用于高闪光强度。此外，还必须知道用于评估样品反射率的光学因素，这是通过在光电导衰减条件下测量稳健的有效寿命值来确定的。最后，还需要了解 c-Ge 中的载流子迁移率，才能将测得的光电导转换为相应的过量载流子密度值。通过将它们与通过微波光电导技术获得的结果进行比较，验证了通过 QSS-PC 技术完成的钝化 c-Ge 衬底的寿命测量。还必须知道用于评估样品反射率的光学系数，这是通过在光电导衰减条件下测量可靠的有效寿命值来确定的。最后，还需要了解 c-Ge 中的载流子迁移率，才能将测得的光电导转换为相应的过量载流子密度值。通过将它们与通过微波光电导技术获得的结果进行比较，验证了通过 QSS-PC 技术完成的钝化 c-Ge 衬底的寿命测量。还必须知道用于评估样品反射率的光学系数，这是通过在光电导衰减条件下测量可靠的有效寿命值来确定的。最后，还需要了解 c-Ge 中的载流子迁移率，才能将测得的光电导转换为相应的过量载流子密度值。通过将它们与通过微波光电导技术获得的结果进行比较，验证了通过 QSS-PC 技术完成的钝化 c-Ge 衬底的寿命测量。