Electron Transport across Vertical Silicon / MoS${_2}$ / Graphene Heterostructures: Towards Efficient Emitter Diodes for Graphene-Base Hot Electron Transistors

TL;DR

This study investigates vertical silicon/MoS2/graphene heterostructures, revealing thermionic emission as the key charge transport mechanism, and suggests their potential as emitter diodes in high-speed graphene-base hot electron transistors.

Contribution

It provides experimental and theoretical insights into thermionic charge transport in Si/MoS2/graphene heterostructures, highlighting their suitability for high-speed electronic applications.

Findings

Thermionic emission confirmed as dominant transport mechanism.

Barrier height linearly dependent on temperature.

Potential application as emitter diodes in hot electron transistors.

Abstract

Heterostructures comprising of silicon (Si), molybdenum disulfide (MoS${_2}$) 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 is compared and fitted to a current transport model that confirms thermionic emission as the responsible transport mechanism across the devices. Theoretical calculations in combination with the experimental data suggest that the heterojunction barrier from Si to MoS${_2}$ is linearly temperature dependent for T = 200 to 300 K with a positive temperature coefficient. The temperature dependence may be attributed to a change in band gap difference between Si and MoS${_2}$, strain at the Si/MoS${_2}$ interface or different electron effective masses in Si and MoS${_2}$, leading to a possible entropy change stemming from variation in density of states as electrons move from Si to MoS${_2}$. The low barrier formed between Si and MoS${_2}$ and the resultant thermionic emission demonstrated here makes the present devices potential candidates as the emitter diode of graphene-base hot electron transistors for future high-speed electronics.