Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states
Abstract
Two key subjects stand out in the pursuit of semiconductor research: material quality and contact technology. The fledging field of atomically thin transition metal dichalcogenides (TMDCs) faces a number of challenges in both efforts. This work attempts to establish a connection between the two by examining the gate-dependent conductance of few-layer (1-5L) WSe2 field effect devices. Measurements and modeling of the subgap regime reveal Schottky barrier transistor behavior. We show that transmission through the contact barrier is dominated by thermionic field emission (TFE) at room temperature, despite the lack of intentional doping. The TFE process arises due to a large number of subgap impurity states, the presence of which also leads to high mobility edge carrier densities. The density of states of such impurity states is self-consistently determined to be approximately 1–2 × 1013/cm2/eV in our devices. We demonstrate that substrate is unlikely to be a major source of the impurity states and suspect that lattice defects within the material itself are primarily responsible. Our experiments provide key information to advance the quality and understanding of TMDC materials and electrical devices.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 13, 2015
- Source ID
- 10.1063/1.4918282
Entities
People
- Daniel Rhodes
- Junjie Wang
- Junqin Zhu
- Kenji Watanabe
- Luis Balicas
- Mauricio Terrones
- Minh An T. Nguyen
- Simin Feng
- Takashi Taniguchi
- Thomas E. Mallouk
Organizations
- Army Research Office
- Florida State University
- Japan Society for the Promotion of Science
- National Institute for Materials Science
- National Science Foundation
- Pennsylvania State University