High growth rate deposition of phosphorus-doped homoepitaxial (001) diamond films for deep-ultraviolet light emitting device

We have characterized P-doped diamond films grown on vicinal (001) high-pressure/high-temperature-synthesized substrates with high growth rate (more than 1 μm/h) using a conventional microwave-plasma chemical vapor deposition apparatus with a quartz-tube chamber, and have fabricated deep-ultraviolet (DUV) light-emitting diodes composed of P-doped (n), undoped (i) and B-doped (p) layers. The P-doped diamond films grown at 1160 °C had the clear cathodoluminescence (CL) peaks at the wavelength of 232.5 and 239 nm which were attributed to the radiative recombination of P-donor bound excitons associated with no phonon emission and a transverse optical phonon emission, respectively. A sharp emission peak was also observed at the wavelength of 235 nm, which was attributed to radiative recombination of a free exciton. These CL features demonstrated rather high quality of the homoepitaxially grown layers. The p-i-n junction whose P-doped layer was grown at 1160 °C had a clear diode characteristic with the rectification ratio of about 103 at ± 20 V. However, some broad CL peaks were additionally observed in the UV and visible regions, indicating that further improvement of crystalline quality of the P-doped diamond film is required for observing monochromatic DUV light emissions.