Resonant-cavity pholodetectors Tor optical communications

摘要

The rapid emergence of high-performance optical systems has accentuated the need for photodiodes with enhanced performance and functionality. In this paper we will describe a new class of photodiodes that utilize novel resonant-cavity structures to achieve high speed, high quantum efficiency, and a narrow spectral response which may prove useful for some wavelength division multiplexing applications. The resonant-cavity photodiode consists of a thin absorbing layer sandwiched between two dielectric mirrors. One advantage of this structure is that it can be utilized to circumvent the responsively/bandwidth tradeoff inherent to conventional PIN photodiodes structures. For the typical normal-incidence photodiode a wide bandwidth necessitates a thin absorption layer which, in turn, results in low quantum efficiency. The resonant-cavity structure, on the other hand, effectively decouples the responsively from the transit-time component of the bandwidth because the optical signal makes multiple passes across the thin absorbing layer inside the microcavity. The resonant-cavity approach has been utilized for p-i-n photodiodes. phototransistors, dual-wavelength photodetectors,7'8 avalanche photodiodes (APOs),9 and Schottky barrier photodiodes.^ In this paper we will concentrate on two specific devices, a Sii_x/Gex resonant-cavity p-i-n photodiode and a resonant-cavity APD with separate absorption and multiplication (SAM) regions.