Porous silicon microcavities fabricated using ion irradiation

By employing microcavity (MC) techniques, the broad spectral band and wide emission angle of photoluminescence from porous silicon (PSi) can be narrowed, directed and tuned in PSi microcavities. The microcavity structure is formed with a porous silicon active layer sandwiched between two Bragg reflectors. We have characterised the optical properties of the porous silicon multilayer structures. A number of Bragg reflectors and Fabry–Perot optical microcavities are fabricated with tuning of emission wavelengths over a wide range in heavily doped p-type silicon. The optical properties of these microstructures were investigated using reflectivity and photoluminescence measurements at different temperatures. This paper reports the ability of focussed 2 MeV proton beam irradiation to controllably blue shift the resonant wavelength of porous silicon microcavities in heavily doped p-type wafers. Using this process wafers are patterned on a micrometer lateral scale with microcavities tuned to different resonant wavelengths, giving rise to high-resolution full-colour reflection images over the full visible spectrum.