Ultra-fast germanium photodiode with 3-dB bandwidth of 265 GHz
Stefan Lischke, Anna Pęczek, Jesse Morgan, Keye Sun, Daniel Steckler, Y. Yamamoto, F. Korndörfer, Christian Mai, S. Marschmeyer, Mirko Fraschke, Andreas Krüger, Andréas Beling, Lars Zimmermann
Abstract
Abstract On a scalable silicon technology platform, we demonstrate photodetectors matching or even surpassing state-of-the-art III–V devices. As key components in high-speed optoelectronics, photodetectors with bandwidths greater than 100 GHz have been a topic of intense research for several decades. Solely InP-based detectors could satisfy the highest performance specifications. Devices based on other materials, such as germanium-on-silicon devices, used to lag behind in speed, but enabled complex photonic integrated circuits and co-integration with silicon electronics. Here we demonstrate waveguide-coupled germanium photodiodes with optoelectrical 3-dB bandwidths of 265 GHz and 240 GHz at a photocurrent of 1 mA. This outstanding performance is achieved by a novel device concept in which a germanium fin is sandwiched between complementary in situ-doped silicon layers. Our photodetectors show internal responsivities of 0.3 A W −1 (265 GHz) and 0.45 A W −1 (240 GHz) at a wavelength of 1,550 nm. The internal bandwidth–efficiency product of the latter device is 86 GHz. Low dark currents of 100–200 nA are obtained from these ultra-fast photodetectors.