Electric-field tunable Type-I to Type-II band alignment transition in MoSe2/WS2 heterobilayers

Jed Kistner-Morris; Ao Shi; Erfu Liu; Trevor Arp; Farima Farahmand; Takashi Taniguchi; Kenji Watanabe; Vivek Aji; Chun Hung Lui; Nathaniel Gabor

doi:10.1038/s41467-024-48321-1

Electric-field tunable Type-I to Type-II band alignment transition in MoSe₂/WS₂ heterobilayers

Nat Commun. 2024 May 14;15(1):4075. doi: 10.1038/s41467-024-48321-1.

Authors

Jed Kistner-Morris^#¹, Ao Shi^#¹, Erfu Liu^{1

2}, Trevor Arp^{1

3}, Farima Farahmand¹, Takashi Taniguchi⁴, Kenji Watanabe⁵, Vivek Aji¹, Chun Hung Lui⁶, Nathaniel Gabor⁷

Affiliations

¹ Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA.
² National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
³ Department of Physics, University of California, Santa Barbara, CA, 93106, USA.
⁴ International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁵ Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁶ Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA. joshua.lui@ucr.edu.
⁷ Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA. nathaniel.gabor@ucr.edu.

^# Contributed equally.

Abstract

Semiconductor heterojunctions are ubiquitous components of modern electronics. Their properties depend crucially on the band alignment at the interface, which may exhibit straddling gap (type-I), staggered gap (type-II) or broken gap (type-III). The distinct characteristics and applications associated with each alignment make it highly desirable to switch between them within a single material. Here we demonstrate an electrically tunable transition between type-I and type-II band alignments in MoSe₂/WS₂ heterobilayers by investigating their luminescence and photocurrent characteristics. In their intrinsic state, these heterobilayers exhibit a type-I band alignment, resulting in the dominant intralayer exciton luminescence from MoSe₂. However, the application of a strong interlayer electric field induces a transition to a type-II band alignment, leading to pronounced interlayer exciton luminescence. Furthermore, the formation of the interlayer exciton state traps free carriers at the interface, leading to the suppression of interlayer photocurrent and highly nonlinear photocurrent-voltage characteristics. This breakthrough in electrical band alignment control, interlayer exciton manipulation, and carrier trapping heralds a new era of versatile optical and (opto)electronic devices composed of van der Waals heterostructures.