Laboratoire de Physique de l'Ecole Normale Supérieure, Ecole Normale Supérieure, Paris Sciences et Lettres, Centre National de la Recherche Scientifique (CNRS), Université de Paris, 24 Rue Lhomond, 75005 Paris, France.
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
Sensors (Basel). 2023 Mar 31;23(7):3635. doi: 10.3390/s23073635.
Charge-sensitive infrared photo-transistors (CSIP) are quantum detectors of mid-infrared radiation (λ=4 µm-14 µm) which have been reported to have outstanding figures of merit and sensitivities that allow single photon detection. The typical absorbing region of a CSIP consists of an AlGaAs quantum heterostructure, where a GaAs quantum well, where the absorption takes place, is followed by a triangular barrier with a graded x(Al) composition that connects the quantum well to a source-drain channel. Here, we report a CSIP designed to work for a 9.3 µm wavelength where the Al composition is kept constant and the triangular barrier is replaced by tunnel-coupled quantum wells. This design is thus conceptually closer to quantum cascade detectors (QCDs) which are an established technology for detection in the mid-infrared range. While previously reported structures use metal gratings in order to couple infrared radiation in the absorbing quantum well, here, we employ a 45° wedge facet coupling geometry that allows a simplified and reliable estimation of the incident photon flux in the device. Remarkably, these detectors have an "auto-calibrated" nature, which enables the precise assessment of the photon flux solely by measuring the electrical characteristics and from knowledge of the device geometry. We identify an operation regime where CSIP detectors can be directly compared to other unipolar quantum detectors such as quantum well infrared photodetectors (QWIPs) and QCDs and we estimate the corresponding detector figure of merit under cryogenic conditions. The maximum responsivity R = 720 A/W and a photoconductive gain G~2.7 × 10 were measured, and were an order of magnitude larger than those for QCDs and quantum well infrared photodetectors (QWIPs). We also comment on the benefit of nano-antenna concepts to increase the efficiency of CSIP in the photon-counting regime.
电荷灵敏红外光电晶体管（CSIP）是中红外辐射（λ=4 µm-14 µm）的量子探测器，据报道，它们具有出色的品质因数和灵敏度，可实现单光子检测。CSIP 的典型吸收区域由 AlGaAs 量子异质结构组成，其中 GaAs 量子阱是吸收发生的地方，其后是具有渐变 x(Al)组成的三角形势垒，将量子阱连接到源漏通道。在这里，我们报告了一种设计用于 9.3 µm 波长的 CSIP，其中 Al 组成保持不变，三角形势垒被隧道耦合量子阱取代。因此，这种设计在概念上更接近量子级联探测器（QCD），QCD 是中红外范围内检测的成熟技术。虽然以前报道的结构使用金属光栅将红外辐射耦合到吸收量子阱中，但在这里，我们采用了 45°楔形面耦合几何形状，可简化和可靠地估计器件中的入射光子通量。值得注意的是，这些探测器具有“自动校准”的特性，仅通过测量电特性并了解器件几何形状，就可以精确评估光子通量。我们确定了 CSIP 探测器可以与其他单极量子探测器（如量子阱红外探测器（QWIP）和 QCD）直接比较的工作模式，并估计了在低温条件下对应的探测器品质因数。测量到的最大响应率 R = 720 A/W 和光电导增益 G~2.7 × 10，比 QCD 和量子阱红外探测器（QWIP）大一个数量级。我们还评论了纳米天线概念在提高 CSIP 在光子计数模式下效率的好处。
