Infrared photodetectors with tailorable response due to resonant plasmon absorption in epitaxial silicide particles embedded in silicon

Abstract

Photodiodes with epitaxial CoSi2 particles embedded in a single-crystal silicon matrix show response in the 1–2 μm range with structure which correlates with absorption peaks due to the surface plasmon resonance of the particles. Aspect ratios (height:diameter) of the particles are accurately controlled by molecular beam epitaxy over a range from 1.4:1 to 1:7, allowing the absorption peaks to be tailored from 1.2 to 2.6 μm, respectively. The particle surface plasmon excitation modifies the photoresponse of the devices and allows this response to be tailored through control of the dimensions of the particles. The photodiodes were tested at 77 K, and 4 of 8 devices tested with an absorption peak at 1.7 μm show dark currents less than 2 nA/cm2 at a reverse bias of 1 V. Detectivities for the same devices at 77 K range from 4×109 to 8×109 cm√Hz/W.