Fig. 3: Graphene/hBN heterostructure phototransistor in the non-linear regime.
a, b Photocurrent as a function of bias (a) and incident power (b) beyond the linear regime. The incident power remains low in a, ranging from 0.1 to 1 mW as well as the bias (20, 50, 90 mV) in b. The measurements are performed at CNP for a temperature of 4 K. The dashed line in a is the extrapolation of the linear regime \(I_{{\rm{PC}}} = aP_{{\rm{inc}}}V_{{\rm{DS}}}^ \ast\). The plain lines in b represent standard saturation laws defined by \(I_{{\rm{PC}}} = aP_{{\rm{inc}}}/(1 + P_{{\rm{inc}}}/P_{{\rm{sat}}})\), with a saturation power Psat ~ 15 mW (Pabs ~ 10 µW) constant for all graphene bias. c Difference ΔIPC between the photocurrent expected for photoconductive regime at large bias (dashed line in a) and the measured photocurrent as a function of \(V_{{\rm{DS}}}^ \ast\) for Pinc ranging from 0.1 to 10 mW clearly showing a threshold behavior. d \(V_{{\rm{DS}}}^ \ast /I_{{\rm{PC}}}\) as a function of bias in logarithmic scale for Pinc ranging from 0.1 to 10 mW; \(V_{{\rm{DS}}}^ \ast /I_{{\rm{PC}}}\) is directly proportional to the total recombination rate Γ(\(V_{{\rm{DS}}}^ \ast\)), itself the weighted sum of the Auger rate Γ1 and HPhP rate Γ2.
