Multiphysics Modeling and Simulation of Carrier Dynamics and Thermal Transport in Monolayer MoS2/WSe2 Heterojunction

Abstract

Computational study of atomically thin monolayer MoS2/WSe2 heterojunction with focus on carrier dynamics and thermal transport is performed by using finite-difference method to solve carrier transport equations and heat conduction equation. Carrier transport in the horizontal direction is in the micrometer scale, while in the vertical direction it is on the subnanometer scale. Carrier transport is modeled as diffusive transport in the horizontal direction with tunneling-assisted carrier recombination between two monolayers in the vertical direction as in the previous study. Band profile, quasi-Fermi level splitting, carrier distribution, and heat generation are investigated in detail. The heterojunction with high-doping concentration has larger current compared to that with low-doping concentration. Heat generation has two components which are due to the Joule heating and inelastic carrier recombination, respectively. The former is provided by the applied voltage, while the latter is from surrounding environment which acts as thermal reservoir. Since the heterojunction works very differently from the conventional p-n diode, it is compared to typical field-effect transistors due to similar device structures. The heat generation of the heterojunction is eight orders lower than that of typical nanoscale field-effect transistors because of its low-current density. Temperature increase in the heterojunction is also several orders of magnitude lower compared to typical nanoscale field-effect transistors.