Lopsided-Gating Leads to Multi-State and Photo-Switching Behaviors With Enhanced Photodetections

In this paper, we propose a new gating scheme that optically turns on a phototransistor by means of a novel structure of lopsided gate. Different from the conventional structure in which the gate electrode overlaps both the source and drain electrodes, the new gate structure is lopsided to form an ungated region between the gate and source, or the gate and drain, allowing light to be detected even in the gate-on state. Furthermore, the proposed gating scheme enables the phototransistor to significantly enhance its photosensitivity as large as 2,200 times higher compared to the baseline in the conventional gate structure. Owing to the optically switching-on behavior in the proposed phototransistor, we also demonstrate that three distinct states can be obtained by a modulation of electrical and optical switches.