Epitaxial MgSnN2 on 4H-SiC (0001): An Earth-Abundant Nitride for Green Optoelectronics and Photovoltaics
Group II-IV nitrides have recently emerged as a novel class of semiconductors composed of earth-abundant elements. Owing to their tunable bandgaps, comparable to those of III-nitrides, these materials are attractive candidates for replacing expensive Ga-based alloys in photovoltaics and green-gap optoelectronics. In this work, epitaxial growth of MgSnN2 layers on 4H-SiC(0001) substrates by direct current magnetron sputtering is demonstrated. Mg and Sn metal targets have been co-sputtered in nitrogen-containing atmosphere at growth temperatures up to 500 {\deg}C. X-ray diffraction and cross-sectional transmission electron microscopy confirm the MgSnN2 layers grow epitaxially in a wurtzite crystal structure, exhibiting the epitaxial relationships with the substrate: MgSnN2 [0001]//4H-SiC [0001] and MgSnN2 [10-10]//4H-SiC[10-10]. Improved crystalline quality is observed for higher deposition temperatures and near-stoichiometric composition, as evidenced by the narrowing of rocking curve linewidths. Optical characterization reveals high absorption coefficients (1e5 cm-1) in the visible spectrum, comparable to that of GaAs, highlighting the suitability of MgSnN2 for photovoltaic applications. A photoluminescence emission band at ~2.4 eV is detected, highly desirable for optoelectronic devices operating in the challenging green spectral region. These results establish MgSnN2 as an earth-abundant, environmentally friendly material, structurally compatible with III-nitrides, with potential for cost-efficient components in sustainable optoelectronics and photovoltaics.