Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride

Abstract

When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

Determination of band offsets at GaN/single-layer MoS2 heterojunction

“…For instance, the first report by Yamada et al has demonstrated the growth of GaN on bulk MoS 2 by molecular beam epitaxy (MBE). 11 There were recent attempts to grow GaN on MoS 2 flakes 10 and layered MoS 2 on GaN epilayers 12 by chemical vapor deposition (CVD) growth techniques. Though the deposition of large area (up to 1 cm 2 ) single-layer (SL) MoS 2 on sapphire exhibiting direct bandgap is achievable, 13 the growth of GaN on such large area MoS 2 monolayers has not yet been explored.…”

Vertical Transistors Based on 2D Materials: Status and Prospects

“…Under many respects, the direct growth/deposition of Gr on the target substrate would be highly desirable. However, to date, high quality Gr growth has been demonstrated only on a few semiconducting or semi-insulating materials, such as silicon-carbide [38][39][40]111,112] and, more Although most of TMD-based devices are still fabricated using exfoliated flakes, much progress has been made in the last few years in the CVD deposition of MoS 2 and other TMDs, both on insulating substrates, such as SiO 2 [121,122] and sapphire [123], and on semiconductors, such as GaN [124]. Noteworthy, an epitaxial registry with the substrate has been observed for CVD-grown MoS 2 on sapphire and on GaN.…”

Large-Scale Synthesis and Systematic Photoluminescence Properties of Monolayer MoS2 on Fused Silica

“…43 The thermal properties of different substrates may have influence on the PL peak energy of MoS 2 monolayer, which has been reported in previous studies. [26][27]44 For both samples, the integrated PL intensity (from the Gaussian fitting result) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 10 / 24 increases with the excitation power under the power law I=L g (Figure 3d), where I is the integrated PL intensity, L is the excitation power, and g represents the growth factor. By curve fitting the experimental data, we extract g to be 0.84 and 0.66 for monolayer MoS 2 on SiO 2 /Si and on fused silica, respectively.…”