Epitaxial growth, structure, and properties of MgZrN₂, an emerging nitride semiconductor

Inorganic nitrides are important technological materials, many of which belong to one of two families: hexagonal main-group metal nitride semiconductors and cubic transition-metal nitride superconductors. We break this dichotomy with our discovery of several new semiconducting Mg-TM-N (TM=Ti, Zr, Hf, Nb, Ta) nitrides which adopt rocksalt crystal structures. Ab-initio calculations on this family of mid-gap semiconductors reveal extremely large dielectric constants (up to 80 ε₀), and a striking tolerance to structural defects relative to other ternary nitrides. This talk will focus on Mg_xZr_2-xN₂. We find that this material forms over a broad metal composition range. At stoichiometric MgZrN₂ compositions, this material behaves as a heavily-doped n-type semiconductor exhibiting a negative temperature coefficient of resistivity and thermally-activated carriers. The transport properties can be radically tuned with Mg:Zr ratio from metallic (Zr-rich) to non-degenerately-doped (Mg-rich). X-ray diffraction and electron microscopy reveal that MgZrN₂ can be epitaxially grown on both GaN and MgO substrates. The combination of elemental abundance, compelling properties, and structural compatibility highlights the potential of these materials for integration with known nitrides.