Voltage-Modulated Operation of MXene Metal–Semiconductor-Metal Photodetectors via Transition of Carrier Transport Mechanism and Developing Dual-Function

In optoelectronics, the charge carrier transport mechanism in metal–semiconductor Schottky contacts is of paramount importance, as it determines the characteristics and performance of photodetectors. However, in practical photodetectors, nonideal photoelectric characteristics may arise due to the coupling and competition between multiple carrier transport mechanisms. Therefore, it is crucial to investigate the underlying mechanisms of this phenomenon to achieve a stable and controllable device operating performance. In this study, we observe a unique alteration in the current–voltage curve of a metal–semiconductor-metal (MSM) photodetector, which is fabricated with Ti3C2Tx MXene symmetric electrodes on a GaAs substrate. The experimental results indicate a substantial light-induced transition in the carrier-transport mechanism within the device. It is demonstrated that light provides additional energy to charge carriers, causing carrier transport to be dominated by the thermionic emission effect rather than the tunneling effect within a low-bias range, while tunneling re-emerges as the dominant mechanism at high biases. The modification of the charge transport mechanism endows the device with complementary characteristics across different bias regimes, enabling dual-function switching via bias modulation to meet diverse application requirements.This work provides a novel pathway for realizing multifunctionality in photodetectors and presents practical approaches to the development of new optoelectronic devices.