Development of Silicon-Based UV-Photodetector Prototypes using Photoluminescent Nanocrystalline Silicon Overlayers

The maximum photoresponse of a normal silicon photodetector, that uses a p-n junction as the active zone, is obtained when the incident radiation wavelength is around 750nm. This response diminishes significantly when the incident radiation is near or in the UV region. Meanwhile, nanocrystalline silicon (nc-Si) films with high transparency above 650nm and high absorbance in the UV can be prepared. By quantum confinement effects, a fraction of this absorbed UV energy is re-emitted as visible photons that can be used by the junction. We study the enhancement of the UV-photoresponse of two silicon detector prototypes with a silicon p-n junction active zone and with a photoluminescent nc-Si overlayer. One prototype is made with a porous silicon/n-type silicon/p-type silicon/p++-silicon/metal configuration and the other with an Eu-doped Si-SiO2 overlayer instead of the porous silicon one. The comparison between both prototypes and the control is presented and discussed stressing on the enhancement effect introduced by the photoluminescent overlayers, stability and reproducibility.