title: Luminescence signature of free exciton dissociation and liberated electron transfer across the junction of graphene/GaN hybrid structure.
abstract: Large-area graphene grown on Cu foil with chemical vapor deposition was transferred onto intentionally undoped GaN epilayer to form a graphene/GaN Schottky junction. Optical spectroscopic techniques including steady-state and time-resolved photoluminescence (PL) were employed to investigate the electron transfer between graphene and n-type GaN at different temperatures. By comparing the near-band-edge excitonic emissions before and after the graphene covering, some structures in the excitonic PL spectra are found to show interesting changes. In particular, a distinct "dip" structure is found to develop at the center of the free exciton emission peak as the temperature goes up. A mechanism that the first dissociation of some freely moveable excitons at the interface was followed by transfer of liberated electrons over the junction barrier is proposed to interpret the appearance and development of the "dip" structure. The formation and evolution process of this "dip" structure can be well resolved from the measured time-resolved PL spectra. First-principles simulations provide clear evidence of finite electron transfer at the interface between graphene and GaN.
authors.affiliation: Department of Physics, HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: 1] Department of Physics, HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong, China [2] Mathematics and Physics Centre, Department of Mathematical Sciences, Xi'an Jiaotong-Liverpool University, Suzhou 215123, China.
authors.forename: Changcheng
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Department of Physics, HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Jiqiang
authors.initials: J
authors.lastname: Ning
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhang
authors.affiliation: 1] State Key Laboratory of Functional Materials for Informatics and Shanghai Center for Superconductivity, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China [2] Department of Physics, State Key Laboratory of Surface Physics and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Physics, Southeast University, Nanjing 211189, China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Ni
authors.affiliation: Department of Physics, State Key Laboratory of Surface Physics and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
authors.forename: Jiannong
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physics, HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Shijie
authors.initials: S
authors.lastname: Xu