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

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 100x100 mu m(2) inverted pyramid device varied over three orders of magnitude (10(-5)-10(-2) W cm(-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 lambda=780 nm) to (1.3 +/- 0.2) A/W at similar to 0.65 mu W. The spectral response profile of the hybrid plasma/semiconductor detector is similar to that of a conventional pn junction photodiode, but is blueshifted by similar to 60 nm. Also, the peak photosensitivity (3.5 A/W at lambda similar or equal to 900 nm) of a Si microplasma device having a 50x50 mu m(2) aperture is approximately twice that for its larger (100x100 mu m(2)) 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. (C) 2005 American Institute of Physics.