Tunable properties of WTe2/GaS heterojunction and Se-doped WTe2/GaS heterojunction

In this paper, geometric properties, electronic natures and optical natures of undoped WTe2/GaS heterojunction and Se atom doped WTe2/GaS heterojunctions are calculated using the Density Functional Theory (DFT). Three most stable heterojunction structures are obtained: A1(undoped WTe2/GaS heterojunction), B1(WTe2/GaS heterojunction with one S atom replaced by one Se atom), and C1(WTe2/GaS heterojunction with one Te atom replaced by one Se atom). By calculating the electronic properties of the heterojunctions, it is concluded that WTe2/GaS heterojunctions of type A1, B1 and C1 are Type-Ⅰ band alignments. When the strength of the external positive electric field is greater than 0.2 V/Å and the compressive stress is greater than 1%, the three kinds of WTe2/GaS heterojunctions become Type-Ⅱ band alignments. Type-Ⅱ band aligns heterojunction is conducive to the separation of photoelectron and hole, and has a wider application. The optical properties of the WTe2 monolayer, the GaS monolayer and three kinds of WTe2/GaS heterojunctions are studied. It is found that the optical absorption coefficients of the three heterojunctions have a slight difference, and the optical absorption coefficients of the WTe2/GaS heterojunctions are higher than those of the two monolayers, indicating that the heterojunctions are more suitable for the production of optoelectronic devices.