A germanium (Ge) or germanium-on-silicon (Ge-on-Si) substrate is an attractive yet not well-studied platform for developing long-wave infrared photonics devices such as lasers and photodetectors. In this paper, we report a long-wave infrared quantum cascade photodetector grown on the Ge substrate with a submonolayer InAs/GaAs quantum dot as the infrared absorber. At 77 K under zero bias, the detector shows a differential-resistance area ($R_{0}A$) product of 298.7 Ω·cm². The normal-incident peak responsivity is 0.56 mA/W observed at 8.3 μm, corresponding to a Johnson noise limited detectivity of 1.5 × 10⁸ cm·Hz^1/2/W. In addition, the effect of the periodic stage number of active regions on device's performance is discussed in detail. The device characteristics presented in this work demonstrate the potential for monolithic integration of this quantum cascade detector with the Ge or Ge-on-Si substrate for large-scale, cost-effective sensing and imaging applications.

中文翻译：

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Ge衬底上生长的亚单层量子点量子级联长波红外光电探测器

锗（Ge）或硅上锗（Ge-on-Si）衬底是开发长波红外光子学设备（如激光器和光电探测器）的诱人但尚未经过充分研究的平台。在本文中，我们报道了一种长波红外量子级联光电探测器，该探测器在Ge衬底上生长，并以亚单层InAs / GaAs量子点作为红外吸收剂。在零偏压下于77 K时，检测器显示出一个差分电阻区域（${\mathrm{[R}}_0\mathrm{一种}$）298.7Ω·cm ^2的乘积。正常入射峰值响应是0.56毫安/ W在8.3观察到 μ米，对应于1.5×10约翰逊噪声的限制探测⁸ 厘米·赫兹^1/2 / W。另外，详细讨论了有源区的周期级数对器件性能的影响。这项工作中提出的器件特性证明了该量子级联检测器与Ge或Ge-on-Si衬底进行单片集成的潜力，可用于大规模，经济高效的传感和成像应用。