The semiconducting properties of diamond make it a material of interest for the fabrication of active electronic devices. Device performance depends on the properties of the host diamond film and the device structure. Improvements in the electronic properties of chemical vapor deposited (CVD) diamond films and in device design are required for development of commercial diamond devices. Hall-effect and capacitance-voltage measurements have been used to assess the electronic quality of diamond films and to evaluate potential device materials and structures.
Homoepitaxial, highly oriented and polycrystalline CVD diamond films have been deposited and characterized by variable-temperature Hall-effect measurements. The highest room temperature hole mobility measured in a homoepitaxial film was 1590 cm2 /V•s where the compensation was ∼2 × 1015 cm-3. These properties are now beginning to approach those of the best type IIb natural diamonds. In a comparison of homoepitaxial, highly oriented diamond film, and polycrystalline diamond films, the room temperature hole mobility was 1470, 229 and 70 cm2/V•s, respectively. This data provides further evidence that the alignment of the grains improves the transport properties of diamond films.
Capacitance-voltage measurements have been performed on single crystal type lib diamond with metal-insulating diamond-semiconducting diamond and metal-oxi de-semiconducting diamond structures. Using a conductance versus frequency technique, the density of interface states was estimated to be ∼1012 cm-2eV-1 for both structures. Although optimization of these structures must still be performed, the ability to measure the interface trap density offers the opportunity to provide direct feedback to the device fabrication process so that the structure may be optimized.