We report on novel InP based traveling wave amplification photodetectors exhibiting an external quantum efficiency of more than 100%. Our detectors vertically combine a bulk InGaAs photodetector ridge region with laterally confined InGaAsP quantum wells for amplification. In addition to ultra high responsivities, such detectors have the potential to also achieve high saturation power and high speed. The device physics is discussed using advanced numerical simulation.
For the past few years, we have been researching a novel type of photodetector featuring distributed optical amplification. We call these devices traveling-wave amplifier-photodetectors, or TAP detectors. The distributed combination of gain and absorption seeks a larger efficiency while keeping a low optical power, thus avoiding saturation. In this paper, we present experimental results both of GaAs- and InP-based TAP detectors, showing in the former case an external quantum efficiency larger than 200%, and larger than 100% in the latter. The performance limitation is shown to be related to the competition between the optical input signal and the amplified spontaneous emission (ASE) generated in the amplifier.
The promising concept of waveguide photodetection with integrated amplification is evaluated by self-consistent device simulation. Such integrated amplification detectors have the potential to achieve simultaneously high saturation power, high speed, high responsivity, and quantum efficiencies well above one. Our example design vertically combines a bulk photodetector ridge region with laterally confined quantum wells for amplification. The current flow in the three-terminal device exhibits ground current reversal with increasing light power. The net optical gain is evaluated for different waveguide modes. For the dominating mode, the detector responsivity is shown to scale with the device length, reaching quantum efficiencies larger than 100%.
High speed, high efficiency, low noise and high saturation power are the characteristics desired for detectors in high bit-rate long-haul optical communication systems. We present the modeling of traveling-wave application photodetectors. These novel monolithic devices combine optical gain and absorption in a distributed fashion along a traveling-wave structure, providing high-responsivity and high-speed performance, without sacrificing saturation power. We present the models used to simulate the behavior of these devices, as well as their result. We show that TAP detectors have higher saturation power than other detectors with the same bandwidth-efficiency product, at the price of a small noise penalty, which is also calculated. The result is a net increase in the dynamic range.
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