Electron Transport across Vertical Silicon/MoS₂/Graphene Heterostructures: Towards Efficient Emitter Diodes for Graphene Base Hot Electron Transistors

Abstract

Heterostructures comprising of 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 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 MoS2 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 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 makes the present devices potential candidates as the emitter diode of graphene-base hot electron transistors for future high-speed electronics.

Correlating Nanocrystalline Structure with Electronic Properties in 2D Platinum Diselenide

“…Vertically aligned layers of PtSe 2 and other 2D dichalcogenides have been reported previously for thicker films. [ 15,48,49 ] The STEM investigations confirm the structural variations as indicated indirectly by the Raman spectroscopic studies discussed earlier.…”

“…for thicker films. [15,48,49] The STEM investigations confirm the structural variations as indicated indirectly by the Raman spectroscopic studies discussed earlier.…”

Correlation of Material Structure and Electronic Properties in 2D Platinum-Diselenide-based Devices

“…Vertically aligned layers of PtSe2 and other 2D dichalcogenides have been reported previously for thicker films. [15,48,49] The STEM investigations confirm the structural variations as indicated indirectly by the Raman spectroscopic studies discussed earlier.…”

Ultrafast Drift Current Terahertz Emission Amplification in the Monolayer WSe2/Si Heterostructure

“…As shown in panels a and b of Figure , a type II band alignment is formed after the heterostructure is built according to the energy bands of monolayer WSe 2 and Si. Electrons transfer from p-type semiconductor WSe 2 to the side of Si, which results in a built-in field at the interface. , To illustrate the amplification mechanism of the drift field in WSe 2 /Si, the depletion layer of the WSe 2 and Si that could accelerate the photoinduced carriers at the interface is shown in Figure c. The polarity of the terahertz emission is determined by the carriers that are related to the doping condition of the semiconductor, indicating that the directions of drift currents from n- and p-type ones are opposite, which gives rise to the drift current of opposite directions. , After the monolayer WSe 2 (p-doped) was transferred to the Si (n-doped) surface, the doping level of the WSe 2 /Si interface could be possibly modified to be p-doped, resulting in the opposite drift current direction of Si with that of WSe 2 and WSe 2 /Si.…”

“…Electrons transfer from p-type semiconductor WSe 2 to the side of Si, which results in a built-in field at the interface. 25,26 To illustrate the amplification mechanism of the drift field in WSe 2 /Si, the depletion layer of the WSe 2 and Si that could accelerate the photoinduced carriers at the interface is shown in Figure 3c. The polarity of the terahertz emission is determined by the carriers that are related to the doping condition of the semiconductor, indicating that the directions of drift currents from n-and p-type ones are opposite, which gives rise to the drift current of opposite directions.…”