Fabrication and characterization of high speed resonant cavity enhanced Schottky photodiodes

Abstract

High speed, high external quantum efficiency and narrow spectral linewidth make resonant cavity enhanced (RC E) Schottky photodetector a good candidate for telecommunication applications. In this thesis, we present our work for the design, fabrication and characterization of a RCE Schottky photodiode with high quantum efficiency and high speed. We present experimental results on a RCE photodiode having an operating wavelength of 900 nm. The absorption takes place in a thin InGaAs layer placed inside the GaAs cavity. The active region was grown above a highreflectivity GaAs/AIAs quarter-wavelength Bragg reflector. The top mirror consisted of a 200A thin Au layer which also acted as Schottky metal of the device. An external quantum efficiency of 55% was obtained from our devices. We demonstrate that the spectral response can be tailored by etching the top surface of the microcavity. Our high speed measurements yielded a FW HM of 30 ps, which is the record response for any RCE Schottky photodiode ever reported.