Electron Transport across Vertical Silicon/MoS₂/Graphene Heterostructures: Towards Efficient Emitter Diodes for...

Heterostructures comprising silicon, molybdenum disulfide (MoS₂), and graphene are investigated with respect to the vertical current conduction mechanism. The measured current-voltage (I-V) characteristics exhibit temperature-dependent asymmetric current, indicating thermally activated charge carrier transport. The data are compared and fitted to a current transport model that confirms thermionic emission as the responsible transport mechanism across devices. Theoretical calculations in combination with the experimental data suggest that the heterojunction barrier from Si to MoS₂ is linearly temperature-dependent for T = 200-300 K with a positive temperature coefficient. The temperature dependence may be attributed to a change in band gap difference between Si and MoS₂, strain at the Si/MoS₂ interface, or different electron effective masses in Si and MoS₂, leading to a possible entropy change stemming from variation in density of states as electrons move from Si to MoS₂. The low barrier formed between Si and MoS₂ and the resultant thermionic emission demonstrated here make the present devices potential candidates as the emitter diode of graphene base hot electron transistors for future high-speed electronics.