Superconductivity and Magnetotransport of MBE grown~Nb$_{\mathrm{2}}$N/SiC and Nb$_{\mathrm{2}}$N/AlN Heterostructures

We find that plasma assisted molecular beam epitaxy (MBE) grown $\beta $-Nb$_{\mathrm{2}}$N thin films [1] are metallic at room temperature, and undergo an electronic phase transition to the superconducting phase below about 10K. Hall-effect measurements reveal a bulk charge density of \textasciitilde 4E23 cm$^{\mathrm{-3}}$ and a mobility of 0.4-0.9 cm$^{\mathrm{2}}$/V.s. Superconducting transition temperature Tc \textasciitilde 10K, in-plane and out of plane critical magnetic field as a function of temperature have been obtained using resistivity and vibrating sample magnetometry measurements. Using this data, an Ioffe-Regel parameter of 10-15, a coherence length of 5-12 nm, and the London penetration depth have been estimated for various thickness of high quality epitaxial Nb$_{\mathrm{2}}$N films. We will contrast transport and structural quality in MBE Nb$_{\mathrm{2}}$N with well-studied NbN by a detailed analysis of aforesaid measurements along with X-Ray diffraction and Transmission-Electron Microscopy data. [1] D.S.Katzer et al., Appl. Phys. Express 8 085501 (2015)