  Nitrides feature many interesting properties, such as a wide range of
bandgaps suitable for optoelectronic devices including light-emitting diodes
(LEDs), and piezoelectric response used in microelectromechanical systems
(MEMS). Nitrides are also significantly underexplored compared to oxides and
other chemistries, with many being thermochemically metastable, sparking
interest from a basic science point of view. This paper reports on experimental
and computational exploration of the Mg-Sb-N material system, featuring both
metastable materials and interesting semiconducting properties. Using sputter
deposition, we discovered a new Mg2SbN3 nitride with a wurtzite-derived crystal
structure and synthesized the antimonide-nitride Mg3SbN with an antiperovskite
crystal structure for the first time in thin film form. Theoretical
calculations indicate that Mg2SbN3 is metastable and has properties relevant to
LEDs and MEMS, whereas Mg3SbN has a large dielectric constant (28\epsilon_0)
and low hole effective masses (0.9m_0), of interest for photovoltaic solar cell
absorbers. The experimental solar-matched 1.3 eV optical absorption onset of
the Mg3SbN antiperovskite agrees with the theoretical prediction (1.3 eV
direct, 1.1 eV indirect), and with the measurements of room-temperature
near-bandgap photoluminescence. These results make an important contribution
towards understanding semiconductor properties and chemical trends in the
Mg-Sb-N materials system, paving the way to future practical applications of
these novel materials.
