Enhanced Photoresponsivity of Multilayer MoS2 Phototransistor Using Localized Au Schottky Junction Formed by Spherical-Lens Photolithography

The photoresponsivity of a MoS2 phototransistor is limited owing to its low light absorption. Many studies aiming to improve the photoresponsivity have enhanced the light absorption in MoS2 by optical resonance or by integrating an absorbing layer. However, the light-absorbing overlayer changes the spectral photoresponsivity and forms a leakage path. In this study, an enhanced photoresponsivity of a multilayer MoS2 phototransistor is obtained by localized Au/MoS2 Schottky junctions without light-absorbing overlayer. Au disks are formed on the MoS2 surface using a simple spherical-lens photolithography technique, forming localized Schottky junctions between MoS2 and Au disks. Photogenerated holes drift to the interface due to the built-in electric field around the Schottky junction and are trapped in the interface states between MoS2 and Au disks. The holes captured in the states lead to photogain. Consequently, after the patterning of the Au disks, the photoresponsivity is enhanced 8.2 times while maintaining other electrical properties. The findings obtained in this study are very valuable as the photoresponsivity enhancement is achieved using the simple method with a minimal damage to MoS2. The multilayer MoS2 phototransistor with Au disks is promising for applications in next-generation optoelectronics with photodetector devices.