Wang J, Wang X, Li Y, Yang Y, Song Q, Xu K. On-chip germanium photodetector with interleaved junctions for the 2-µm wave band.
OPTICS LETTERS 2024;
49:1085-1088. [PMID:
38359259 DOI:
10.1364/ol.515378]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/25/2024] [Indexed: 02/17/2024]
Abstract
Recently, the 2-µm wave band has gained increased interest due to its potential application for the next-generation optical communication. As a proven integration platform, silicon photonics also benefit from the lower nonlinear absorption and larger electro-optic coefficient. However, this spectral range is far beyond the photodetection range of germanium, which places an ultimate limit for on-chip applications. In this work, we demonstrate a waveguide-coupled photodetector enabled by a tensile strain-induced absorption in germanium. Responsivity is greatly enhanced by the proposed interleaved junction structure. The device is designed on a 220-nm silicon-on-insulator and is fabricated via a standard silicon photonic foundry process. By utilizing different interleaved PN junction spacing configurations, we were able to measure a responsivity of 0.107 A/W at 1950 nm with a low bias voltage of -6.4 V for the 500-μm-long device. Additionally, the 3-dB bandwidth of the device was measured to be up to 7.1 GHz. Furthermore, we successfully achieved data transmission at a rate of 20 Gb/s using non-return-to-zero on-off keying modulation.
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