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 CH 4 in microwave plasma assisted chemical vapor deposition (CVD) using CH 4 , 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 µA 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.