Influence of surface crystal-orientation on transfer doping of V2O5/H-terminated diamond

Surface transfer doping of hydrogen-terminated diamond induced by high work function V2O5 oxide was investigated on samples with (100) and (111) surface crystal-orientations. An enhancement of sheet hole density and a decrease in sheet resistance were obtained in the case of (111) diamond as compared to (100). In particular, a sheet resistance as low as 1.8 k?/? and a sheet hole concentration of 1.1 ? 1014 cm-2 were obtained by Hall effect measurements for V2O5/H-(111) oriented diamonds, the latter being about twice as high as the one obtained for V2O5/H-(100) oriented diamonds. This was confirmed by capacitance-voltage measurements on metal/V2O5/H-diamond diodes fabricated on the investigated samples, also resulting in the determination of the depth profiles of hole accumulation layers at the diamond surface. X-ray photoelectron spectroscopy measurements of the C1s core level shift were used to determine the differences in surface band bending, leading to a different hole accumulation layer formation efficiency at the V2O5/H-diamond interface. An upward band bending of 0.7 eV and 0.3 eV in response to the surface transfer doping induced by a 10 ? thick V2O5 layer was measured for (111) and (100) diamond surfaces, respectively. This is a further confirmation that V2O5 is more effective in surface transfer doping for H-(111) oriented diamond. The obtained results are very promising in view of the development of high-power metal oxide field effect transistors based on the H-diamond surface.