Crystalline silicon carbon nitride: A wide band gap semiconductor

Crystalline thin films of SiCN have been grown by microwave plasma-enhanced chemical vapor deposition using ${\mathrm{H}}_{\mathrm{2}},$ ${\mathrm{CH}}_{\mathrm{4}},$ ${\mathrm{N}}_{\mathrm{2}},$ and ${\mathrm{SiH}}_{\mathrm{4}}$ gases. The ternary compound $(\mathrm{C;Si}{)}_x{\mathrm{N}}_y$ exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the compound is about 35–40 at. %, the extent of Si substitution varies and can be as low as 10 at. %. Optical properties of the SiCN compounds have been studied by photoluminescence (PL), piezoreflectance (PzR), and photothermal deflection (PDS) spectroscopies. From the PzR measurement, we determine the direct band gap of the new crystals to be around 3.8 eV at room temperature. PDS measurement shows two absorption features with the first peak at around 3.2 eV which is related to an indirect band gap. The second PDS peak occurred around 3.8 eV and is quite consistent with the direct band gap determined by PzR. From the PL measurement, it is also found that the SiCN compounds have a near band edge emission centered around 3.26 eV at room temperature, which is consistent with the fundamental band gap obtained from the PDS measurement. These optical results indicate the potential of SiCN for blue and uv optoelectronic applications.