Effects of Carrier Gas on Carbon Incorporation in GaN

GaN epitaxial layers were grown on Si (111) substrates by metal organic chemical vapor deposition. Carbon concentrations in the films grown in different ambients were measured by secondary ion mass spectrometry. The results show that the carbon incorporation is strongly dependent on the H₂ flow rate when the NH₃ flow rate is small, but insensitive to the H₂ flow rate when the NH₃ flow rate is sufficient large. We conclude that H₂ can inhibit the dissociation of NH₃ and result in a less active N source; an insufficiently active N source causes more N vacancies, which enhances carbon incorporation.