Emerging colloidal quantum dot (cQD) photodetectors currently challenge established state-of-the-art infrared photodetectors in response speed, spectral tunability, simplicity of solution processable fabrication, and integration onto curved or flexible substrates. Hybrid phototransistors based on 2D materials and cQDs, in particular, are promising due to their inherent photogain, enabling direct photosignal enhancement. The photogain is sensitive to both measurement conditions and photodetector geometry. This makes the cross-comparison of devices reported in the literature rather involved. Here, the effect of device length L and width W scaling to subwavelength dimensions (sizes down to 500 nm) on the photoresponse of graphene-PbS cQD phototransistors was experimentally investigated. Photogain and responsivity were found to scale with 1/LW, whereas the photocurrent and specific detectivity were independent of geometrical parameters. The measurements were performed under scaled bias voltage conditions for comparable currents. Contact effects were found to limit the photoresponse for devices with L < 3 μm. The relation of gate voltage, bias current, light intensity, and frequency on the photoresponse was investigated in detail, and a photogating efficiency to assess the cQD-graphene interface is presented. In particular, the specific detectivity values in the range between 10⁸ and 10⁹ Jones (wavelength of 1550 nm, frequency 6 Hz, room temperature) were found to be limited by the charge transfer across the photoactive interface.

中文翻译：

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将混合量子点-石墨烯光电探测器缩放至亚波长尺寸

目前，新兴的胶体量子点 (cQD) 光电探测器在响应速度、光谱可调性、溶液加工制造的简单性以及在弯曲或柔性基板上的集成方面对现有的最先进的红外光电探测器提出了挑战。基于 2D 材料和 cQD 的混合光电晶体管尤其具有前景，因为它们具有固有的光电增益，可以直接增强光信号。光电增益对测量条件和光电探测器的几何形状都很敏感。这使得文献中报道的设备的交叉比较变得相当复杂。在这里，通过实验研究了器件长度L和宽度W缩放至亚波长尺寸（尺寸小至 500 nm）对石墨烯-PbS cQD 光电晶体管的光响应的影响。发现光增益和响应度与 1/ LW成比例，而光电流和特定探测率与几何参数无关。测量是在可比较的电流的缩放偏置电压条件下进行的。研究发现，接触效应限制了L < 3 μm 器件的光响应。详细研究了栅极电压、偏置电流、光强度和频率对光响应的关系，并提出了评估 cQD-石墨烯界面的光选通效率。特别是，发现10 ⁸和10 ⁹ Jones（波长1550 nm，频率6 Hz，室温）之间的特定探测率值受到跨光活性界面的电荷转移的限制。