High-Speed Internal Photoemission Detectors Enhanced by Grating Coupling to Surface Plasma Waves

Abstract

The use of gratings to couple optical energy into surface plasma wave (SPW) modes that are confined to a metal-dielectric boundary has been extensively explored [1]. With optimal choices of the grating period and profile, nearly 100% coupling efficiency has been achieved in wavelength ranges where the metal is normally almost totally reflecting. We report the use of this coupling to enhance the quantum efficiency of internal-photoemission detectors in which hot carriers, generated in a metal film by optical absorption, are collected by photoemission over a Schottky barrier into a semiconductor. This class of detectors is of interest as a result of its uniformity, high-speed potential, long wavelength response with binary rather than quaternary III–V compounds, and compatibility with integrated circuit fabrication techniques [2–4]. For metal-silicide/Si systems, which have been the most thoroughly explored, techniques such as back-illumination and double-pass insulator-metal overlayer structures already provide quite high absorption (> 40%) at infrared wavelengths. Surface texturing has also been used to enhance the responsivity of metal-insulator-metal tunnel junction detectors and of metal-(a-Si)-metal detectors [5,6].

This research was supported by the Department of the Air Force, in part with specific funding from the Air Force Office of Scientific Research.