Abstract
A novel waveguide-coupled germanium p-i-n photodiode is demonstrated which combines high responsivity with very high -3 dB bandwidth at a medium dark current. Bandwidth values are 40 GHz at zero bias and more than 70 GHz at -1 V. Responsivity at 1.55 µm wavelength ranges from 0.84 A/W at zero bias to 1 A/W at -1 V. Room temperature dark current density at -1 V is about 1 A/cm2. The high responsivity mainly results from the use of a new, low-loss contact scheme, which moreover also reduces the negative effect of photo carrier diffusion on bandwidth.
Highlights
Germanium (Ge) p-i-n photodiodes, coupled to a silicon waveguide, are the most widely used light detecting elements in technologies for Si-based photonic integrated circuits (PIC) or electronic photonic integrated circuits
The high responsivity mainly results from the use of a new, low-loss contact scheme, which reduces the negative effect of photo carrier diffusion on bandwidth
To obtain a low-resistive CoSi2 layer, as it is common in CMOS or BiCMOS processes, silicide process modules typically include two anneal steps with the second one featuring a temperature of 700 °C or even higher [10]
Summary
Germanium (Ge) p-i-n photodiodes, coupled to a silicon waveguide, are the most widely used light detecting elements in technologies for Si-based photonic integrated circuits (PIC) or electronic photonic integrated circuits (ePIC). To obtain a low-resistive CoSi2 layer, as it is common in CMOS or BiCMOS processes, silicide process modules typically include two anneal steps with the second one featuring a temperature of 700 °C or even higher [10]. Under such anneal conditions an as-implanted P profile in Ge can significantly be broadened by diffusion [11]. Key for high responsivity is a new, low-loss contact scheme, which, reduces the bandwidth-limiting effect of photo carrier diffusion
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