Detection of infrared photons using the electronic stress in metal-semiconductor interfaces

Abstract

.It is well known that the work function of metals de-es when they are pIaced in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photons using the stress caused by pho~o-electrons emitted tim a metal film surfme in contact with a semiconductor microstructure. The photoelectrons diffuse into the microsticture and produce an electronic stress. The photon detection results fiorn the measurement of the photo-induced bending of the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due toelectronic stress. Small changes in position (displacement) of microstructure are routineIy measured in atomic force microscop y (AFlvl) where atomic imaging of surfaces relies on the measurement of small changes (< 10"'m) in the bending of microcantilevers. In the present work we studied the photon response of Si microcantiIevers coated with a thin film of Pt. The Si microcantiievers were 500 nm tii~and had a 30 mn layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interfhce which diffise into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to conmct in length but not the F%layer, the bimaterial microcantilever bends. In our present stdies we used the optical detection technique to measure the photometric response of Pt-Si microcantikwers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength A =1550 nm.

Modeling of Photoinduced Deformation in Silicon Microcantilever

“…Similar effects were also found in some ceramic materials [4],and can be used as photostrictive actuators [5, 6]. Under that effect, the photogeneration of free charge carriers (electrons and holes) in a semiconductor, results in the development of a local mechanical strain [1, 7, 8]. In the late 1990s, Datskos's team investigated the photostriction effect in a silicon microcantilever structure [1, 7, 8].…”

“…Under that effect, the photogeneration of free charge carriers (electrons and holes) in a semiconductor, results in the development of a local mechanical strain [1, 7, 8]. In the late 1990s, Datskos's team investigated the photostriction effect in a silicon microcantilever structure [1, 7, 8]. It was also applied in photon detection [1, 7, 8] and chemical gas sensing [9].…”

“…In the late 1990s, Datskos's team investigated the photostriction effect in a silicon microcantilever structure [1, 7, 8]. It was also applied in photon detection [1, 7, 8] and chemical gas sensing [9]. They constructed a basic theory of the photostriction effect in a semiconductor cantilever structure.…”

“…They constructed a basic theory of the photostriction effect in a semiconductor cantilever structure. Their assumption was that the density of the photoinduced excess carriers was homogeneous in the microcantilever, shown by the average density they used to calculate photoinduced strain in equations 2 and 3 in reference [1, 7, 8]. However, their theoretical results were about 25 times larger than the experimental values [1, 7, 8].…”

“…Their assumption was that the density of the photoinduced excess carriers was homogeneous in the microcantilever, shown by the average density they used to calculate photoinduced strain in equations 2 and 3 in reference [1, 7, 8]. However, their theoretical results were about 25 times larger than the experimental values [1, 7, 8]. In this study, by considering the spatial distribution and surface recombination of photoinduced carriers in silicon, we have constructed a model for prediction the photoinduced deformation in a microcantilever structure.…”