Vertical 2D/3D Semiconductor Heterostructures based on Epitaxial Molybdenum Disulfide and Gallium Nitride
Dmitry A. Ruzmetov, Kehao Zhang, Gheorghe Stan, Berc Kalanyan, Ganesh R. Bhimanapati, Sarah M. Eichfeld, R A. Burke, Pankaj B. Shah, Terrance P. O'Regan, Frank J. Crowne, A. Glen Birdwell, Joshua A. Robinson, Albert Davydov, Tony G. Ivanov
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 (MoSub2) directly on gallium nitride (GaN) resulting in high-quality, unstrained, single-layer MoS(sub2) 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 heterostructure, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS(sub2) monolayer triangles average 1 um along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single crystal MoS(sub2) sheets. Photoluminescence, Raman, atomic force microscopy, and x-ray photoelectron spectroscopy analysis identified monolayer MoS(sub2) with a prominent 20-times enhancement of photoluminescence in the center regions of larger triangles. The MoS(sub2)/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 MoS(sub2)/GaN contact resistivity to be less than 4 ohm-cm(superscript 2) and current spreading in the MoS(sub 2) monolayer of approximately 1 um in diameter.