Investigation of breakdown properties in the carbon doped GaN by photoluminescence analysis.

The electrical and optical properties of the carbon doped GaN grown on Si substrate by metal-organic chemical-vapor deposition are investigated. Carbon impurity doping can improve the breakdown voltage effectively. However excess carbon in contrast depresses the breakdown voltage. This result is correlated with the carbon dopant behaviour in GaN which can be observed by analyzing the photoluminescence (PL) spectra. It is explained that the carbon impurity favours the formation of CN (carbon substitution of nitrogen) which acts as a deep level acceptor. The acceptor compensates the n-type background impurities, which may resulting in suppressing the leakage current at high electric field, and leads to the improvement of the breakdown voltage. However, with excess carbon doping level, a significant amount of C_Ga (carbon substitution of gallium) form in GaN. The C_Ga, acting as the donor, compensates the C_N and hence impairs the concentration of the deep level acceptor. In a result, the compensation of the n-type background impurities by the deep level acceptor is curbed by the C_Ga-C_N self-compensation effect, which leads to the decrease of the breakdown voltage. [ABSTRACT FROM AUTHOR]