Capacitance-voltage measurements on metal-SiO2-diamond structures fabricated with (100)- and (111)-oriented substrates

Metal-SiO₂-diamond structures fabricated using (100)- or (111)-oriented substrates of type IIb natural diamond (a p-type semiconductor) are discussed. The SiO₂-diamond interface was electrically characterized by measuring the capacitance between the metal electrode and the diamond substrate as a function of bias voltage. Capacitance-voltage (C-V) characteristics were measured for various SiO₂ thicknesses and substrate temperatures, with and without exposure to ultraviolet light. For (100)-oriented diamond substrates, the SiO₂-diamond interface is of device quality, and the minimum conduction-band energy of diamond is found to be 1.4 eV below that of SiO₂. For (111)-oriented substrates this energy for diamond is 1.6 eV above that for SiO₂ and 0.7 eV above the vacuum level. From these results, it appears that useful depletion-mode, metal-SiO₂-diamond FETs can be made on (100)-oriented diamond substrates and that (111)-oriented substrates may be of value as cold cathodes