Thin Film Synthesis of Semiconductors in the Mg-Sb-N Materials System

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 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 (28ϵ₀) and low hole effective masses (0.9m₀), 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 toward understanding semiconductor properties and chemical trends in the Mg-Sb-N materials system, paving the way to future practical applications of these novel materials.