Transport in Complex Crystalline Materials Based on van der Waals Heterostructures

Report No. ARL-TR-8756
Authors: Mahesh R Neupane, Dmitry Ruzmetov, A Glen Birdwell, Robert Burke, Ryan Enck, Michael Daniel Valentin, Edward Byrd, Matthew Chin, and Tony Ivanov
Date/Pages: August 2019; 164 pages
Abstract: A dearth of high-quality 2-D semiconductors and the difficulty of scaling down 3-D semiconductors have severely limited the prospects for the development of next-generation energy efficient electronic devices. To overcome these challenges, we have developed a technique to integrate van der Waals 2-D and conventional 3-D semiconductors. Our resultant novel 2-D/3-D heterostructure consists of molybdenum disulfide as the 2-D component encapsulated between 3-D gallium nitride in a vertical configuration. This ultra-thin structure is a promising material system as a component of an improved heterojunction bipolar transistor (HBT). High-quality, defect-free interfaces between the 2- and 3-D systems, a critical criterion for efficient HBT device operation, was achieved through chemical powder vaporization, metal-organic chemical vapor deposition, and molecular beam epitaxy. We also synthesized a trilayer 3-D/2-D/3-D semiconductor structure (the first demonstration of its kind), validated all major critical aspects of the design, and performed a feasibility study of our design and microfabrication process for a functional HBT model. In particular, 2-D/3-D diode behavior was demonstrated for the fully synthesized heterostructures built without mechanical transfer. The outcomes of this basic research effort could pave the way for explorations into the novel physics of 2-D materials for energy-efficient electronics devices and systems.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2019