High-speed 1.55 μm operation of low-temperature-grown GaAs-based resonant-cavity-enhanced p-i-n photodiodes

We report the design, growth, fabrication, and characterization of GaAs-based high-speed p-i-n photodiodes operating at 1.55 mum. A low-temperature-grown GaAs (LT-GaAs) layer was used as the absorption layer and the photoresponse was selectively enhanced at 1.55 mum using a resonant-cavity-detector structure. The bottom mirror of the resonant cavity was formed by a highly reflecting 15-pair GaAs/AlAs Bragg mirror. Molecular-beam epitaxy was used for wafer growth, where the active LT-GaAs layer was grown at a substrate temperature of 200degreesC. The fabricated devices exhibited a resonance around 1548 nm. When compared to the efficiency of a conventional single-pass detector, an enhancement factor of 7.5 was achieved. Temporal pulse-response measurements were carried out at 1.55 mum. Fast pulse responses with 30 ps pulse-width and a corresponding 3 dB bandwidth of 11.2 GHz was measured. (C) 2004 American Institute of Physics.