Anisotropic Superconductivity of InN Grown by Molecular Beam Epitaxy on Sapphire (0001)

We report a study of anisotropic superconductivity of InN grown by MBE on a sapphire (0001) surface. InN shows a resistivity anomaly below 3.5 K and a superconductivity below 1.5 K. The superconductivity is of the second kind and its Hc1 and Hc2 are 0.08 and 0.8 T, respectively, when the magnetic field (B) is applied parallel to the c-axis. When B ∥ c-axis, Hc1 and Hc2 are 0.23 and 2.3 T, respectively. InN demonstrates negative magnetoresistance above Hc2 and the resistivity decreases 4% at 12 T under the B ∥ c-axis configuration. These results indicate that the superconductivity of InN is anisotropic.