Nonlinear effects excitonic emission from high quality homoepitaxial diamond films

A nonlinear relationship between the intensity of the free-exciton emission (235 nm) and the electron-beam current has been observed in cathodoluminescence (CL) spectra from homoepitaxial diamond films for the first time at room temperature. For high quality diamond films grown using a low concentration of CH4 in microwave plasma assisted chemical vapor deposition (CVD) using CH4, the excitonic emission intensity increases linearly with the electron bean current in the low excitation region but increases super-linearly in the high excitation region above a threshold value of about 30 mu A at room temperature. These results strongly suggest that the free-exciton emission from high quality diamond films is able to apply as a light souse for deep-ultraviolet (235 nm) of light emitting diodes and laser diodes.