Photodetectors Based on 3D Self-Assembled Ge and Si Micro-Crystals

The direct epitaxial growth of silicon and germanium on silicon (Ge-on-Si) has fostered the development of visible - near-infrared detectors for telecom and imaging applications. A viable route to enhance the responsivity of such photodetectors might be exploiting the micro-structuring of the absorbing layer to increase the effective volume of interaction between light and matter. In this work we report on a new type of detectors, obtained from Si and Ge micro-crystals epitaxially grown on a patterned Si substrate [2,3]. The faceted morphology and relatively high aspect ratio of the micro-crystals is seen to enhance the fraction of absorbed light and the detector responsivity as compared to conventional planar devices. This enhancement is present in the indirect regime of absorption of Ge, for the Ge micro-crystals, and in the NIR for the Si micro-crystals.