Abstract
We studied the relationship between the absorption layer length and the performance of Ge-on-Si microring resonator photodetectors. The principle of optimizing the absorption layer length based on the light field distribution was proposed. In the Ge-on-Si photodetectors, the transmission light field is alternately distributed among the germanium absorption layer and the silicon waveguide layer, and gradually absorbed by the germanium layer. For the Ge-on-Si microring resonator photodetectors, the length of the germanium absorption layer should be set to achieve the maximum light field distribution in the silicon layer at the end of the photodetector, then the remaining optical power can be coupled back to the silicon waveguide and transmit in the microring for absorption again. We demonstrated by simulation that, the device with optimized length of 11 μm has larger bandwidth, smaller dark current, and higher responsivity than the device with 14 μm absorption layer by simulation <email xlink:type="simple" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> @1550nm.
Highlights
For the optical communication and interconnect system, the photodetector is a key device for receiver part
We studied the relationship between the absorption layer length and the performance of Ge-on-Si microring resonator photodetectors
In the Ge-on-Si photodetectors, the transmission light field is alternately distributed among the germanium absorption layer and the silicon waveguide layer, and gradually absorbed by the germanium layer
Summary
For the optical communication and interconnect system, the photodetector is a key device for receiver part. The III-V devices require a high cost and are not compatible with the Complementary Metal Oxide Semiconductor (CMOS) technology for large-scale integration. Silicon-based optoelectronic devices arouse an extensively research interest in recent years because of ease of integration and low cost [5]–[9]. Germanium photodetectors are compatible with CMOS technology. In the Ge-on-Si. photodetectors’ design, the short germanium absorption layer has a small capacitance and lower electrode loss, so a larger bandwidth can be realized. High responsivity requires a long germanium absorption layer. The responsivity enhanced Ge-on-Si microring resonator photodetectors by increasing absorption times have been reported [18]–[21]. The reported improvement of the microring photodetectors’ performance is still not significant, which is caused by the unoptimized length of the germanium absorption layer. If the absorption length is not optimized, most remaining optical power after the first absorption would be scattered and reflected, which is not coupled to the silicon waveguide of microring for multiple absorption
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