On-chip Ge, InGaAs, and colloidal quantum dot photodetectors: comparisons for application in silicon photonics

Abstract

The past twenty years have seen explosive growth in silicon photonics technology. It has revolutionized numerous fields such high-speed optical interconnects in data centers. A photodetector (PD) is one of the key building blocks in silicon photonics, enabling on-chip light detection. Here a comprehensive study has been demonstrated in which three materials, germanium (Ge), indium gallium arsenide (InGaAs), and colloidal quantum dots (CQD), are compared for a PD integrated with a waveguide in silicon photonics. Comparisons are conducted by assuming InGaAs and CQD PDs have the same interface quality as mature Ge PD technology. With this premise, we intend to predict future InGaAs and CQD PD performances. Figures of merit such as dark current, responsivity, and RF bandwidth are compared using simulations. With the premise that epitaxial InGaAs on silicon is as of high quality as epi-Ge, results found that the InGaAs PD is advantageous over the Ge PD with higher-efficiency bandwidth product and lower dark current. CQD PD, on the other hand, is slow but has the lowest dark current, which is suitable for medium-speed applications where ultralow noise is required.