Holmium-doped porous silicon prepared by a new electrochemical approach and its photoluminescence

Porous silicon (PS) was found to emit visible luminescence at room temperature. This phenomenon implies a potential application of silicon in optoelectronics. The luminescence of PS can be improved by doping with rare earth elements. A new electrochemical doping approach, constant-potential electrolysis, and a new electrolyte system for doping of porous silicon with holmium were reported. By this approach and system, the doping products were well controlled, and He-doped PS(HDPS) was found to emit much intenser visible photoluminescence with blueshift in wavelength and higher luminescence stability at room temperature than that for corresponding PS wafer. The effects of various kinds of holmium compounds, solvents, applied voltage, concentration of holmium nitrate and doping time on photoluminescence of HDPS were investigated, and the optimum doping conditions were fixed. The luminescence mechanisms for PS and HDPS were discussed.