Interface Structure and Doping of Chemical Vapor Deposition‐Grown MoS₂ on 4H–SiC by Microscopic Analyses and Ab Initio Calculations

Abstract

The interface structure and electronic properties of monolayer (1L) MoS2 domains grown by chemical vapor deposition on 4H–SiC(0001) are investigated by microscopic/spectroscopic analyses combined with ab initio calculations. The triangular domains are epitaxially oriented on the (0001) basal plane, with the presence of a van der Waals (vdW) gap between 1L–MoS2 and the SiC terraces. The high crystalline quality of the domains is confirmed by photoluminescence emission. Furthermore, a very low tensile strain (ε ≈ 0.03%) of 1L–MoS2, consistent with the small in‐plane lattice mismatch, and a p‐type doping of (0.45 ± 0.11) × 1013 cm−2, is evaluated by Raman mapping. Density functional theory (DFT) calculations of the MoS2/4H–SiC(0001) system are also performed, considering different levels of refinement of the model: 1) the simple case of the junction between Si‐terminated SiC and MoS2, showing a covalent bond between the Si–S atoms and n‐type doping of MoS2; 2) the complete passivation of Si dangling bonds with a monolayer (1 ML) of oxygen atoms, resulting in a vdW bond with dSi–S ≈ 3.84 Å bond length and p‐type doping of MoS2; and 3) partial (¼ ML and ½ ML) oxygen coverages of the 4H–SiC surface, resulting in intermediate values of dSi–S and doping behavior.

Interface Properties of MoS2 van der Waals Heterojunctions with GaN

“…The interface properties of the 2D/3D vdW heterostructure were characterized by cross-sectional transmission electron microscopy analyses. Figure 6a is an overview HR-TEM image, showing a monolayer MoS 2 conformal to the crystalline GaN substrate, similarly to other reports for MoS 2 grown by CVD approaches on GaN or other crystalline hexagonal substrates [36,37,80,81]. Furthermore, the presence of a vdW gap between the single layer of MoS 2 and GaN surface is clearly demonstrated by the high-resolution HAADF-STEM image in Figure 6b.…”

Advances and challenges in 4H silicon carbide: defects and impurities

“…For example, titanium, a common metal impurity in SiC, produced very shallow electronic energy levels near the conductive band edge (E C −0.11/0.17 eV) of 4H-SiC crystals [149]. Oxygen is also a general impurity in nearly all semiconductor materials including silicon, and may also be present in 4H-SiC crystals [150,151]. Avoiding intentionally doping is important to improve the quality of 4H-SiC [152,153].…”