Ferroelectric Tailorable WS2/Graphene Phototransistors.

Abstract

Two-dimensional (2D) phototransistors face severe challenges in achieving high photoresponsivity and low power consumption, primarily due to their low absorption cross-section and short carrier lifetime, especially as the device feature size continues to shrink. To address these challenges, we propose a ferroelectric-enhanced doping effect to conduct band engineering and charge redistribution, which effectively mitigates the Fermi level pinning effect and enables selective ambipolar behaviors, resulting in ideal electrical contact and efficient carrier transport. Furthermore, the polarization-induced floating gate introduces additional gain mechanisms through defect engineering and a tunneling effect, which significantly improves photomultiplication and carrier acceleration. Consequently, the as-fabricated phototransistor based on a WS₂/graphene heterojunction and Al:HfO₂ ferroelectric layer exhibits outstanding performances, including a high detectivity of 2.38 × 10¹³ Jones and an impressive photogain of 3.28 × 10⁷, without requiring an external gate bias. These exceptional multifaceted characteristics highlight the potential of the proposed ferroelectric-tailored device for applications in integrated circuits, optoelectronic logic operations, and image sensors.