Gate-tunable photodetector and ambipolar transistor implemented using a graphene/MoSe2 barristor

Next-generation electronic and optoelectronic devices require a high-quality channel layer. Graphene is a good candidate because of its high carrier mobility and unique ambipolar transport characteristics. However, the on/off ratio and photoresponsivity of graphene are typically low. Transition metal dichalcogenides (e.g., MoSe2) are semiconductors with high photoresponsivity but lower mobility than that of graphene. Here, we propose a graphene/MoSe2 barristor with a high-k ion-gel gate dielectric. It shows a high on/off ratio (3.3 × 104) and ambipolar behavior that is controlled by an external bias. The barristor exhibits very high external quantum efficiency (EQE, 66.3%) and photoresponsivity (285.0 mA/W). We demonstrate that an electric field applied to the gate electrode substantially modulates the photocurrent of the barristor, resulting in a high gate tuning ratio (1.50 μA/V). Therefore, this barristor shows potential for use as an ambipolar transistor with a high on/off ratio and a gate-tunable photodetector with a high EQE and responsivity. An approach that enhances control over charge carrier movement in graphene-based transistors may be useful in applications such as bendable circuits and light sensors. The difference in current flow when a transistor turns from on to off plays a critical role in determining device performance. Bae Ho Park from Konkuk University in Seoul, South Korea, and colleagues report that stacking graphene on top of another two-dimensional (2D) film of molybdenum selenide can lead to larger on/off current ratios than conventional graphene transistors. Optical and electrical characterizations revealed that the interface between the 2D films created a potential barrier that blocked current flow in the device’s off state without compromising graphene’s mechanical flexibility. Using an external voltage to modulate current flow through the barrier region also allowed the stacked device to serve as a high-efficiency photodetector. we report a field-effect device with a graphene/MoSe2 channel layer and high-k ion-gel gate dielectric. The device shows a high carrier mobility (~247 cm2/V ∙ s), a high on/off ratio (3.3 × 104), and ambipolar behavior that are controlled by an applied gate voltage. The strong gating effect of the device results in higher external quantum efficiency (EQE) (66.3%), photoresponsivity (285.0 mA/W), and gate-tuning ratio (1.50 μA/V) compared to pristine devices. Therefore, our graphene/MoSe2 barristor device can be a suitable candidate for use in ambipolar transistors and gate-tunable broad-area photodetectors.