Microcavity plasma photodetectors: Photosensitivity, dynamic range, and the plasma-semiconductor interface

Abstract

Detailed measurements of the photosensitivity of Si microcavity plasma photodetectors in the visible and near-infrared (420–1100 nm) are reported for input optical intensities to a 100×100μm2 inverted pyramid device varied over three orders of magnitude (10−5–10−2Wcm−2). By resolving the contribution to the overall device response from the plasma/semiconductor interaction, as opposed to bulk Si photoconductivity, the photosensitivity of the plasma photodetector operating in 500 Torr of Ne was determined to range from (2.2±0.4)A∕W for 2 nW of input power (at λ=780nm) to (1.3±0.2)A∕W at ∼0.65μW. The spectral response profile of the hybrid plasma/semiconductor detector is similar to that of a conventional pn junction photodiode, but is blueshifted by ∼60nm. Also, the peak photosensitivity (3.5A∕W at λ≃900nm) of a Si microplasma device having a 50×50μm2 aperture is approximately twice that for its larger (100×100μm2) counterpart under identical conditions. Analysis of the data suggest that bandbending at the p-Si surface is sufficiently strong for a thin n-type region to form, thereby resembling a metal-oxide-semiconductor capacitor in the inversion mode. Electrons in this thin layer tunnel through the vacuum (Si-plasma) barrier, followed by electron avalanche in the nonequilibrium plasma. These results illustrate the potential for novel optoelectronic devices when interfacing a plasma with a semiconductor and coupling the two media with a strong electric field imposed across the interface.