Tunable infrared photoemission sensor on silicon using SiGe/Si and silicide/Si epitaxial layers

Abstract
We present a new type of infrared detector on Si whose cut-off wavelength is tuned by an externally applied bias. This tunable internal photoemission sensor (TIPS) consists of two different conducting materials (metal or degenerately doped SiGe) separated by a thin undoped Si layer. The two conducting materials are chosen with different barrier heights on Si so that the depleted Si layer forms an asymmetrical potential barrier. Under sub-band gap illumination, carriers (both holes and electrons) which are photocreated in each conducting film, cross the Si barrier and give rise to a photocurrent between the two electrodes. This photocurrent is strongly dependent on the shape and height of the Si potential barrier that can be varied by a small bias applied between the two electrodes. In this paper, the TIPS principle of operation and the photoresponse tunability are demonstrated using both the Ir/Si/ErSi₂ and Cr/Si/SiGe (p+) heterostructure.