A semiconductor pixel unit for sensing near-infrared light, and for optionally simultaneously sensing visible light. The pixel unit comprises a single substrate with a first semiconductor region and a second semiconductor region electrically separated by an insulating region, for example a buried oxide layer. The pixel unit is adapted for generating a lateral electrical field in the second region for facilitating transport of photoelectrons generated in the second region by near-infrared light passing through the first region and the insulating region.