The Ir/Si/ErSi2 tunable infrared photoemission sensor

We present a new type of metal-silicon-metal infrared detector, the tunable infrared photoemission sensor (TIPS), whose photoresponse can be tuned by an externally applied bias. The physical detection process of this new device is based on the internal photoemission of optically excited carriers between the two metal layers of the vertical Ir/Si/ErSi₂/Si_sub system. We show that the experimental TIPS cut-off wavelength is shifted from around 2 urn to more than 6 urn with a quantum efficiency of 3% at 2 |i,m and more than 1% at 3 urn when a bias of less than IV is applied to the Ir electrode. The experimental quantum efficiency of such a heterostructure is quantitatively explained using a model derived from the Fowler photoemission formalism, taking into account the wavelength dependence of light absorbed in each metallic film and the four different photoemission processes present in the TIPS structure. Dark current measurements of the TIPS structure indicate that high detectivities (above 10¹⁰ cm√Hz /W at 2µm at 125K) may be expected with this new type of device.