Photocapacitance measurements on MOS light emitting devices

The photocapacitance (PC) has been probed on MOS diodes with an Eu-implanted SiO2 layer. In general, rare earth implanted SiO2 layers in MOS diodes are of great interest for possible applications in integrated metal-oxide-semiconductor light emitting devices (MOSLEDs). For example, green and ultraviolet electroluminescence has been probed on SiO2:Tb-MOSLEDs and SiO2:Gd-MOSLEDs, respectively. MOSLEDs reach external quantum efficiencies between 1% and 16%, and the electroluminescence peaks are typically ascribed to 4f-intrashell transitions of trivalent rare earth ions. A clear capacitance change has been observed for different wavelengths under monochromatic illumination. Some of the detected peaks correspond to the energies of 4f-intrashell transitions of the Eu ions. According to this, the number of active luminescence centers in MOSLEDs may be determined from PC measurements. Some 4f-intrashell transitions have been also observed by means of electroluminescence measurements on the same MOSLEDs. To emphasize the physical significance of the PC data recorded on SiO2:Eu-MOSLEDs, we also compare PC data recorded on different MOSLEDs implanted with other rare earth ions.