Zero-bias 40Gbit/s germanium waveguide photodetector on silicon

Abstract

We report on lateral pin germanium photodetectors selectively grown at the end of silicon waveguides. A very high optical bandwidth, estimated up to 120GHz, was evidenced in 10 µm long Ge photodetectors using three kinds of experimental set-ups. In addition, a responsivity of 0.8 A/W at 1550 nm was measured. An open eye diagrams at 40Gb/s were demonstrated under zero-bias at a wavelength of 1.55 µm.

50 Gb/s Silicon Photonics Receiver With Low Insertion Loss

“…This agrees with the ePIXfab quoted specification. It was found that the current had no dependence on the applied bias, similar to Vivien et al [17] observed, which implies that all of the photogenerated carriers are collected by the strong built-in electric field.…”

“…The difference in amplitude for each channel can be attributed to the non-uniform gain of the EDFA. The data rate from each channel could be further improved by integration with the Vivien et al [17] 40 Gb/s photodetectors also fabricated at LETI. These devices have a narrower intrinsic width of 500 nm which decreases the carrier transportation time.…”

“…Germanium was then deposited in these recesses using a selective reduced pressure chemical vapour deposition (RP-CVD) process. A chemical mechanical polishing step (CMP) was carried out to planarize the surface following germanium overgrowth which was necessary in order to prevent faceting in the recesses [17]. SiO 2 was then deposited and patterned to define the ion implantation windows needed to form the p-i-n junctions.…”

“…Germanium has a bandgap of 0.66 eV meaning the absorbing region extends slightly beyond 1.55 µm. Waveguide integrated photodetectors have been demonstrated by a number of groups with both vertical [6][7][8][9][10][11][12][13][14][15] and lateral [16][17][18] device designs.…”

All silicon approach to modulation and detection at λ = 2 µm

“…On the component level, a large amount of research is ongoing worldwide to achieve increased levels of performance in different metrics such as speed, power consumption, modulation depth, footprint, wavelength independence, temperature insensitivity, and optical loss. Photodetection has typically been achieved at NIR wavelengths in germanium [6][7][8][9] , with high performance waveguide integrated devices now considered a mature process.…”