May 2018
Spotlight Summary by Lan Fu
Size reduction of Ge-on-Si photodetectors via a photonic bandgap
Monolithically integrated Ge-on-Si photodetectors are highly desirable for achieving Si-based photonic integration or infrared sensing at low cost and low power consumption. This requires the development of small-footprint photodetectors to reduce dark current (and thus noise) and increase electric bandwidth, at the same time without compromising the detector responsivity as the fundamental trade-off with the reduction of optical absorption volume. In this paper, the authors propose a new Ge-on-Si photodetector design by surrounding the epitaxially grown Ge photodetector on Si with a photonic crystal structure fabricated in the Si slab. As a result, the radiation modes from those non-absorbed guided outgoing waves can be effectively prohibited facilitating light cyclic absorption in the epitaxial Ge region. By numerical design and optimization of the photonic crystal structure to obtain a photonic bandgap with a width of ~400 nm at a central wavelength of 1550 nm, this work has experimentally demonstrated a highly compact 5-μm-long, low dark current (150 nA), high bandwidth (17 GHz at 3 dB) Ge-on-Si photodetector with a high and broadband responsivity comparable to that of an 8 x 25 μm2 baseline Ge device. The research provides a useful pathway for development of ultracompact photodetectors realized in ultra-small cavities with photonic bandgap effect.
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Article Information
Size reduction of Ge-on-Si photodetectors via a photonic bandgap
Haifeng Zhou and Yiling Sun
Appl. Opt. 57(12) 2962-2966 (2018) View: Abstract | HTML | PDF