High-Mobility and High-Responsivity MoS2 Phototransistor Enabled by Rippled Mg Substrate Engineering

The 2-D semiconductors, such as molybdenum disulfide (MoS2), have seen extensive use in the fields of electronics and optoelectronics. However, the lower carrier mobility and weak light absorption ability of the ultrathin layered structure greatly limit commercial applications. In this study, we use a single-step UV-ozone oxidation method to transform flat magnesium (Mg) into a rippled substrate, which effectively enhances the carrier mobility of MoS2 from the range of $19.2\sim 31.2$ to $45.3\sim 78.2$ cm ${}^{{2}} \cdot $ V ${}^{\text {-1}} \cdot $ s ${}^{\text {-1}}$ . Owing to the multiple reflections from peak to peak, the device also demonstrates high photoresponsivity of $1.6\times 10^{{5}}$ A/W. Interestingly, with appropriate gate bias, the device exhibits constant photoresponsivity of ~220 A/W independent of the incident light intensity. This work presents a simple oxidation-induced rippled Mg substrate, which simultaneously addresses low carrier mobility and weak light absorption in 2-D semiconductors, enabling synergistic electrical-optical improvements, paving the way for the design of high-performance optoelectronic devices.