Electrical and light-emitting properties from (111)-oriented homoepitaxial diamond p–i–n junctions

We have succeeded in fabricating a (111)-oriented diamond p–i–n junction with high crystalline quality intrinsic layer and with low series resistance. The series resistance of this diamond p–i–n junction was improved by decreasing the resistivity and specific contact resistance of n-type layer, which is allowed to inject higher current while maintaining lower junction temperature. Current density–voltage characteristics showed a rectification ratio of 106 at ± 15 V at room temperature. A clear ultraviolet emission at around 235 nm due to free exciton recombination was observed at a forward current, while the broad visible light emission from deep levels was significantly suppressed. Moreover, stronger excitonic emission by two orders of magnitude than that of (001)-oriented diamond p–i–n junctions with high series resistance was realized.