Ultra-low dark current self-powered metal-graphene-metal photodetector based on photo-thermoelectric (PTE) effect

The performance of relevant detectors may be limited by the high dark current, low noise equivalent power, and photo-response. Graphene is a promising choice for low light intensity detection as a two-dimensional material. In this paper, a self-powered metal-graphene-metal photodetector with a 1 nm graphene layer, working in the range of 0.1–0.3 μm is designed and evaluated, which can be used in the free space optical communication, wearable modules, and imaging. The main mechanism governing the detection process is the photo-thermoelectric effect, an indirect method in which the incident light energy is initially converted to thermal energy and consequently to an electric potential due to the resulting temperature gradient. The large dark current is one major problem with the conventional metal-semiconductor-metal photodetectors. The proposed structure provides an ultra-low dark current density as low as 1.5 × 10^− 20 A/cm² and, thereby, a very low thermal noise of I_Johnson=5 × 10^− 22 A, which can be attributed to the high Schottky barrier in the graphene/contact interface. In addition, the responsivity of about 0.0453 A/W and the detectivity of 6.52 × 10¹⁷ Jones are obtained for the proposed photodetector, comparable to the characteristics of the conventional photodetectors using two-dimensional materials.