Ohmic and Schottky contacts of hydrogenated and oxygenated boron-doped single-crystal diamond with hill-like polycrystalline grains

Hill-like polycrystalline diamond grains (HPDGs) randomly emerged on a heavy boron-doped p⁺ single-crystal diamond (SCD) film by prolonging the growth duration of the chemical vapor deposition process. The Raman spectral results confirm that a relatively higher boron concentration (～ 1.1×10²¹ cm^-3) is detected on the HPDG with respect to the SCD region (～ 5.4×10²⁰ cm^-3). It demonstrates that the Au/SCD interface can be modulated from ohmic to Schottky contact by varying the surface from hydrogen to oxygen termination. The current-voltage curve between two HPDGs is nearly linear with either oxygen or hydrogen termination, which means that the HPDGs provide a leakage path to form an ohmic contact. There are obvious rectification characteristics between oxygen-terminated HPDGs and SCD based on the difference in boron doping levels in those regions. The results reveal that the highly boron-doped HPDGs grown in SCD can be adopted as ohmic electrodes for Hall measurement and electronic devices.