Light coupling mechanism of quantum grid infrared photodetectors

Rigorous electromagnetic modeling based on a modal solution of the pertinent boundary-value problem was performed to study the light coupling mechanism in quantum grid infrared photodetectors with lamellar patterns. Our theory shows that vertical field component and absorption quantum efficiency eta can be strongly enhanced by judiciously adjusting the width w of individual grid lines. This enhancement is further increased if the top of the grid lines is covered by metal, which behave as a collection of dipole scatterers. We have experimentally verified the dipole scattering characteristics with different w, and found that the variation of eta agrees very well with the theory. We also found that, as expected, the conductivity of the metal strips affects eta significantly due to internal dissipation. (C) 2002 American Institute of Physics.