where R is the responsivity (A W -1 ), A is the device area (cm 2 ), in is the noise current (A Hz -1/2 ), BW is the measurement bandwidth, and NEP is the noise equivalent power. For accurate characterization the specific detectivity was calculated additionally from the NEP (5×10 -14 W) and the equivalent noise bandwidth (ENBW) of the lock-in, which defines the measurement bandwidth, resulting in a similar specific detectivity of 9.7×10 Jones. The ENBW is dependent on the filter settings and the measurement time constant, for our measurements 0.094 Hz. At a modulation frequency of 27 Hz, the specific de-tectivity will exceed 10 10 Jones. In comparison with room temperature measurements of the same detector, the specific detectivity is nearly 10 times higher at 80 K. Even though the specific detectivity of state-of-the-art epitaxial grown InGaAs photodetectors is still superior to our hybrid devices, the latter bear advantages for potentially low-cost fabrication, CMOS compatibility, scalability, and-at the same time-the spectral sensitivity can readily be tuned by QD materials and sizes. Further improvements of the specific detectivity may be achieved by increasing the light absorption cross-section of the QD thin film and further noise reduction. A looped transconductance measurement at 80 K reveals gate-voltage-dependent hysteresis of the device (Figure ), which can be quenched under constant illumination with energies above the QD bandgap but persists at lower photon energies. Gate voltage induced hysteresis at room temperature for graphene FETs is assigned to trapping and de-trapping of charges in the gate oxide in proximity to the graphene channel. Here, charge carriers most likely are being transferred and accumulated in the QD thin film at low temperatures, resulting in the hysteresis, which can be quenched by photo-induced charge carrier accumulation in the QD thin film. This supports that the interface between graphene and the QD thin film is gate-dependent and does not freeze out at low temperatures. In Summary, QD/graphene FETs have been fabricated and characterized over a wide range of temperatures and gate voltages. While a decrease in photoresponse is expected at lower temperatures due to freezing out the temperature-driven charge carrier transfer over the potential barrier, we have found the opposite: a complex temperature-and gate-voltage-behavior with the highest photoresponse at 80 K. Surface alterations, such as surface oxidation, proved to have a significant influence on the temperature-and gate-voltage-dependence. Hence, these measurements could be utilized for QD surface analytics. Interestingly, the charge carrier type transferred from the QD layer to the graphene under illumination can switch its sign, depending on the temperature and gate voltage, which may be explained with temperature-sensitive surface dipoles resulting in a temperature-driven shift of the conduction-and valence bands consequentially altering the band alignment to graphene. Detectors fabricated from less oxidized QDs with less surface trap states have shown to be faster with the highest photoresponse and specific detectivity of 10 10 Jones at the wavelength and temperature of 1280 nm and 80 K, respectively. Our findings open a new measurement methodology for hybrid photodetectors leading to a better understanding of charge transfer between QDs and 2D materials not just for photodetectors, but also for other QD-based optoelectronic devices.