Comparison of the electric properties of single-crystal and polycrystalline diamond by Hall effect and capacitance-voltage measurements
The transport properties of type IIb (naturally B-doped), single-crystal diamond were investigated by differential capacitance-voltage (C-V) measurements, Hall effect measurements and resistivity measurements. The results for the Hall effect and resistivity measurements on single-crystal samples were compared with similar measurements on polycrystalline samples grown by microwave-assisted chemical vapor deposition. The C-V and Hall effect measurements on single crystal, type IIb diamond samples showed consistent results. Temperature-dependent resistivity measurements verified an activation energy of 0.36 eV, while room temperature Hall effect measurements on a (100)-oriented, type IIb single crystal indicated that the active carrier concentration was 2.1×1013 cm-3. This result was consistent with total B concentrations measured by both C-V and secondary ion mass spectroscopy (SIMS). The transport properties for polycrystalline samples were not as good as those for single-crystal samples. At room temperature, the mobilities were 3 and 10 cm2 V-1 s-1 for two in situ doped polycrystalline thin films, as compared with 325 cm2 V-1 s-1 for the single-crystal sample. For one in situ doped sample, the activation energy was measured to be 0.05 eV and the room temperature carrier concentration was 1.8×1016 cm-3, while SIMS indicated that the total atomic B concentration was 5×1018 cm-3. The relatively low carrier concentrations measured in the polycrystalline samples may be indicative of a high level of compensation (about 65%) or trapping of charge at the grain boundaries, leading to a depletion of carriers in the crystallites.
von Windheim, JA; Venkatesan, V; Malta, DM; Das, K
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