Influence of waveguide structural on performance of SiGe ridge waveguide phototransistor

Abstract

The emerging hot industries such as 5G communications require a higher demand for Si-based photo detectors, especially the SiGe heterojunction phototransistor with internal gain. But there is a big contradiction between the responsivity optimization and working speed promotion. These cause the difficulty of optimizing the common vertical-illustrated SiGe phototransistor. This paper proposed a novel SiGe ridge waveguide phototransistor and analyzed the influence of the waveguide structure, including base thickness, ridge waveguide width and length, on its optical characteristic frequency and optical gain. The ridge waveguide structure is optimized and obtained finally. When the thickness of the base region is 40nm, the doping concentration is 1.0×10¹⁹cm^-3, the waveguide length is 50μm, and the ridge width is 1μm, the designed SiGe ridge waveguide phototransistor obtained the optical gain of 6.24 and the maximum characteristic frequency of 12.8GHz under incident light of 850nm.