Structural, electronic, and polarization properties of YN and LaN

Semiconducting ScN has attracted significant scientific and technological interest; however, similar III-Nitrides such as YN and LaN are largely unexplored. To help fill this gap, we compare the structural and electronic properties of ScN, YN, and LaN. We find all three to have band gaps around 1 eV in their rocksalt phases, with only LaN having a direct band gap. ScN and YN both have higher-energy layered hexagonal structures; however, LaN prefers to adopt the polar wurtzite structure, which we show to be lower in energy than the rocksalt structure, and thus likely to be experimentally accessible. We calculate its polarization, along with its piezoelectric and ferroelectric properties. Wurtzite LaN has a smaller switching barrier than Al_xSc_1-xN alloys, lending it to potential use in ferroelectric devices. In addition, we show that wurtzite LaN and zincblende InP are close to lattice matched, and forming a heterostructure between them will result in a large bound charge of 1.3×10¹⁴ e/cm², which could be used in tunnel junction devices.

This work was supported by DOE, AFOSR, and NSF, and was performed under the auspices of the DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.