Toward the Modulation of Temperature Dependence of Photoresponse in Heterojunctions: Synergistic Effects from Carrier Trapping and Mobility Competition Dynamics

The optimal operating temperature for photodetectors is generally determined by noise-restraining demands rather than by achieving the best photoresponse. Simultaneous optimization of both noise and photoresponse is difficult due to limitations in material characteristics. The photogating effect in heterojunction devices provides a possible way to modulate the optimal operating temperature for noise and photoresponse separately in different material layers. This study proposes a band engineering paradigm for fabricating semiconductor heterostructures, wherein systematic investigations reveal the synergistic modulation of the photoresponse peak temperature through competitive carrier trapping-detrapping dynamics and temperature-dependent mobility variations, ultimately achieving directional regulation of the photoresponse peak temperature. Experimental results demonstrate that the pure lead sulfide device exhibits a pronounced photocurrent peak at 250 K, whereas the peak shifts approximately 50 K toward lower temperatures after integration with graphene. For the germanium/graphene heterostructure, its shallow trap energy level induces an earlier equilibrium between carrier mobility and trap release rate, thereby further shifting the photoresponse peak to ultralow temperatures (<100 K). In contrast, due to the deeper trap energy level, the silicon/graphene heterostructure extends the mobility-dominated region to beyond 300 K, successfully achieving the high-temperature extension of the photoresponse peak. This study introduces a paradigm for manipulating carrier dynamics in photodetector design, particularly for specialized operational environments, which holds potential value for applications such as infrared remote sensing.