Epitaxial Growth of ZnGa₂O₄: A New, Deep Ultraviolet Semiconductor Candidate

ZnGaO films were grown on c-plane sapphire substrates by metal organic chemical vapor deposition using diethylzinc (DEZn), triethylgallium (TEGa), and oxygen. The flow rate of DEZn was 10-60 sccm, and those of TEGa and oxygen were held constant. The ZnGaO film prepared at a DEZn flow rate of 10 sccm adopted a (201)-oriented single-crystalline β-Ga₂O₃ phase, whereas those prepared at 30-60 sccm exhibited a (111)-oriented single-crystalline ZnGa₂O₄ phase. On the basis of Hall measurements, ZnGaO films (10 sccm DEZn) possessed very poor electrical properties, which were similar to those of β-Ga₂O₃. On the other hand, the carrier concentration in ZnGaO films increased from 1.94 × 10¹⁴ to 6.72 × 10¹⁶ cm^-3, and the resistivity decreased from 5730 to 67.9 ω-cm when increasing the DEZn flow rate from 30 to 60 sccm. According to compositional analyses, the improved electrical properties of ZnGaO films upon increasing DEZn flow rate from 30 to 40 sccm are due to the increasing Zn content, and the enhancement from 50 to 60 sccm could be due to increased C content. Cathodoluminescence results also confirm the ZnGa₂O₄ structure for ZnGaO films prepared at DEZn flow rates of 30-60 sccm and reveal their use for ultraviolet applications.