J. Mater. Sci. Technol. ›› 2025, Vol. 207: 76-85.DOI: 10.1016/j.jmst.2024.04.030

• Research article • Previous Articles     Next Articles

Origin of two-dimensional hole gas at the hydrogen-terminated diamond surfaces: Negative interface valence-induced upward band bending

Qingzhong Guia, Wei Yua, Chunmin Chengb, Hailing Guoa, Xiaoming Zhaa, Ruyue Caoc, Hongxia Zhongd, John Robertsona,c, Sheng Liub,e, Zhaofu Zhangb,e,f,*, Zhuo Jianga,*, Yuzheng Guoa,b,f,*   

  1. aSchool of Electrical Engineering and Automation, Wuhan University, Wuhan 430072, China;
    bThe Institute of Technological Sciences, Wuhan University, Wuhan 430072, China;
    cDepartment of Engineering, Cambridge University, Cambridge, CB2 1PZ, United Kingdom;
    dSchool of Mathematics and Physics, China University of Geosciences, Wuhan 430074, China;
    eHubei Key Laboratory of Electronic Manufacturing and Packaging Integration, Wuhan University, Wuhan 430072, China;
    fResearch Institute of Wuhan University in Shenzhen, Shenzhen 518057, China
  • Received:2023-12-21 Revised:2024-03-14 Accepted:2024-04-22 Published:2025-02-01 Online:2024-05-08
  • Contact: *E-mail addresses: zhaofuzhang@whu.edu.cn (Z. Zhang), zhuojiang@whu.edu.cn (Z. Jiang), yguo@whu.edu.cn (Y. Guo)

Abstract: The surface transfer doping model has been extensively adopted as a mechanism to account for the generation of hole accumulation layers below hydrogen-terminated diamond (H-diamond) surfaces. To achieve effective surface transfer doping, surface electron acceptor materials with high electron affinity (EA) are required to produce a high density of two-dimensional hole gas (2DHG) on the H-diamond subsurface. We have established ingenious theoretical models to demonstrate that even if these solid materials do not have a high EA value, they remain capable of absorbing electrons from the H-diamond surface by forming a negatively charged interface to act as a surface electron acceptor in the surface transfer doping model. Our calculations, particularly for the local density of states, provide compelling evidence that the effect of an interface with negative charges induces an upward band bending on the H-diamond side. Furthermore, the valence band maximum of the diamond atoms at the interface crosses the Fermi level, giving rise to strong surface transfer p-type doping. These results give a strong theoretical interpretation of the origin of 2DHG on H-diamond surfaces. The proposed guidelines contribute to further improvements in the performance of 2DHG H-diamond field effect transistors.

Key words: Hydrogen-terminated diamond, Surface transfer doping, Two-dimensional hole gas, First-principles calculations