Ionic Glass–Gated 2D Material–Based Phototransistor: MoSe2 over LaF3 as Case Study

Modulating the carrier density of 2D materials is pivotal to tailor their electrical properties, with novel physical phenomena expected to occur at a higher doping level. Here, the use of ionic glass as a high capacitance gate is explored to develop a 2D material–based phototransistor operated with a higher carrier concentration up to 5 × 10¹³ cm^?2, using MoSe₂ over LaF₃ as an archetypal system. Ion glass gating reveals to be a powerful technique combining the high carrier density of electrolyte gating methods while enabling direct optical addressability impeded with usual electrolyte technology. The phototransistor demonstrates I_ON/I_OFF ratio exceeding five decades and photoresponse times down to 200 µs, up to two decades faster than MoSe₂ phototransistors reported so far. Careful phototransport analysis reveals that ionic glass gating of 2D materials allows tuning the nature of the carrier recombination processes, while annihilating the traps' contribution in the electron injection regime. This remarkable property results in a photoresponse that can be modulated electrostatically by more than two orders of magnitude, while at the same time increasing the gain bandwidth product. This study demonstrates the potential of ionic glass gating to explore novel photoconduction processes and alternative architectures of devices.