Determining the Electronic Structure and Thermoelectric Properties of MoS2/MoSe2 Type-I Heterojunction by DFT and the Landauer Approach

Abstract

The electronic structure and thermoelectric properties of MoX2 (X = S, Se) Van der Waals heterojunctions are reported, with the intention of motivating the design of electronic devices using such materials. Calculations indicate the proposed heterojunctions are thermodynamically stable and present a band gap reduction from 1.8 eV to 0.8 eV. The latter effect is highly related to interactions between metallic d-character orbitals and chalcogen p-character orbitals. The theoretical approach allows to predict a transition from semiconducting to semi-metallic behavior. The band alignment indicates a type-I heterojunction and band offsets of 0.2 eV. Transport properties show clear n-type nature and a high Seebeck coefficient at 300 K, along with conductivity values (σ/τ) in the order of 1020. Lastly, using the Landauer approach and ballistic transport, the proposed heterojunctions can be modeled as a channel material for a typical one-gate transistor configuration predicting subthreshold values of ≈60 mV dec−1 and field–effect mobilities of ≈160 cm−2 V−1 s−1.