Frequency response and bandwidth enhancement in Ge/Si avalanche photodiodes with over 840GHz gain-bandwidth-product

Abstract

In this work we report a separate-absorption-charge-multiplication Ge/Si avalanche photodiode with an enhanced gain-bandwidth-product of 845 GHz at a wavelength of 1310 nm. The corresponding gain value is 65 and the electrical bandwidth is 13 GHz at an optical input power of -30 dBm. The unconventional high gain-bandwidth-product is investigated using device physical simulation and optical pulse response measurement. The analysis of the electric field distribution, electron and hole concentration and drift velocities in the device shows that the enhanced gain-bandwidth-product at high bias voltages is due to a decrease of the transit time and avalanche build-up time limitation at high fields.

High sensitivity 10Gb/s Si photonic receiver based on a low-voltage waveguide-coupled Ge avalanche photodetector

“…It can be seen that the GBP reaches a plateau at -5.8V (~100GHz), after which it further increases due to bandwidth enhancement as seen in Fig. 3(b), similar to what is reported in [16]. The 100GHz GBP is comparable to standard InPbased APDs [5].…”

A silicon avalanche photodetector fabricated with standard CMOS technology with over 1 THz gain-bandwidth product

“…Figure 2 shows measured current-voltage characteristics of the fabricated CMOS-APD with and without optical illumination. The avalanche breakdown voltage can be defined as the voltage at which the dark current reaches 10 μA [6,7], and, with this definition, the avalanche breakdown voltage of the CMOS-APD is about 10.7 V. When the reverse bias voltage is small, the CMOS-APD has low photocurrents of about 0.5 μA. With the reverse bias voltage approaching the avalanche breakdown voltage, photocurrents start to increase dramatically with internal gain provided by the avalanche multiplication process.…”

“…In order to realize CMOS EPICs for optical interconnects, implementation of high-speed and high-responsivity photodetectors is required. Germanium-based photodetectors have been investigated due to their large absorption coefficient at 1.3-μm and 1.5-μm wavelengths as well as compatibility with CMOS technology [6][7][8]. Another interesting approach is using standard CMOS technology without any modifications for 850-nm photodetector realization.…”

High speed InAs electron avalanche photodiodes overcome the conventional gain-bandwidth product limit

“…Figure 2 illustrates that there is significant potential for increasing gain-bandwidth products by reducing k. Kang et al [23] exploited this approach, using a silicon multiplication region with k ~0.08 to achieve a record gain-bandwidth product limit for high bandwidth APDs, despite their APD having a much larger w than state-of-the-art III-V APDs. Further characterization of these devices by Zaoui et al [24] under higher biases showed that nonlocal effects can increase the bandwidth further; however under these conditions the leakage current rose to become orders of magnitude higher than the photocurrent. .…”