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Title: 3D Band Diagram and Photoexcitation of 2D–3D Semiconductor Heterojunctions

The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. In this paper, we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS2 and p-type Si, in which the conduction and valence band-edges of the MoS2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriers inside the device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron–hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the “on/off” states of the junction photodetector device. Finally, two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [5] ;  [1] ;  [6] ;  [1] ;  [1] ;  [1] ;  [7] ;  [1] ;  [1]
  1. Rice Univ., Houston, TX (United States). Dept. of Materials Science and NanoEngineering
  2. Rice Univ., Houston, TX (United States). Dept. of Materials Science and NanoEngineering; Lanzhou Univ. (China). School of Physical Science and Technology
  3. Rice Univ., Houston, TX (United States). Dept. of Electrical and Computer Engineering; Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
  4. Rice Univ., Houston, TX (United States). Dept. of Chemistry
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  6. Northeastern Univ., Boston, MA (United States). Dept. of Mechanical and Industrial Engineering
  7. Rice Univ., Houston, TX (United States). Dept. of Materials Science and NanoEngineering; Rice Univ., Houston, TX (United States). Dept. of Electrical and Computer Engineering; Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
Publication Date:
OSTI Identifier:
1265614
Grant/Contract Number:
AC05-00OR22725; W911NF-11-1-036; FA9550-14-1-0268
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 15; Journal Issue: 9; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); US Department of Defense; Air Force Office of Scientific Research (AFOSR) (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY band diagram; charge generation; exciton relaxation; MoS2-Si heterojunction