A Novel Wavelength Tunable Silicon Detector for Infrared Detection

Abstract

A cryogenic extrinsic silicon detector which can detect IR photons of very low energy, i.e., down to about 5.5 meV ( 220 μm) is presented. The mechanism involves photoexcitation of carriers over low energy interfacial work function barriers at p-i or n-i interfaces in a process analogous to the classic photoelectric effect. Estimates for the responsivity and the detectivity for unoptimized commercial samples containing both p-i and n-i interfaces and a sample containing only a single p-i interface are provided by comparison with a silicon composite bolometer. The range of long wavelength thresholds (λ_t) observed suggests that this approach can be used to tailor detectors for different IR wavelength regions by changing the dopant impurity and the impurity concentration at levels near the metal-insulator transition. Single interface results confirm the possibility of detector optimization using multilayered structures. This should lead to a unique family of uniform monolithic IR focal plane structures with tailorable and tunable response characteristics within virtually all the IR spectral range of interest.