Suppression of noise in semiconductor infrared detectors using plasmonics

Abstract

We consider the enhancement of the specific detectivity of semiconductor infrared photodetectors for the mid-infrared range utilizing spherical submicrometer plasmonic particles with redshifted spectral characteristics. The optical field is strongly concentrated near the plasmonic particle located on top of the detector active area; thus, the necessary thickness of the device is significantly reduced. In order to ensure the plasmonic effect in infrared, we apply a redshifting strategy based on the simultaneous use of doped transparent conductive oxides (TCO) with a lower plasma frequency compared to metals and an embedding high-permittivity dielectric that further redshifts the spectral characteristics. A graded antireflective layer with a linear increase of the refractive index is applied on top of the structure. We perform ab initio simulation of the optical response of the whole system utilizing the finite element method. As an illustrative example, we analyze a mercury cadmium telluride infrared detector with an epitaxial active layer. We observe suppression of the overall generation-recombination (g-r) noise level (Auger, radiative and Shockley-Read) due to the decrease of the volume of the active region. The specific detectivity of the system is simultaneously increased by optical field localization (light management) and by noise suppression. An elevation of the operating temperature of the detector is observed as a result. According to our simulations, a specific detectivity enhancement of more than an order of magnitude should be readily achievable.