Abstract
Silicon photonics has recently been proposed for a diverse set of applications at mid-infrared wavelengths including spectroscopy, chemical and biological sensing, free-space communications, and nonlinear optics. While optical-to-electronic signal conversion is essential to these applications, on-chip photodetection remains an important and challenging task. In this Letter, we present room temperature operation of Zn+-implanted Si waveguide photodiodes from 2.2 to 2.4 μm, with measured responsivities of up to 87±29 mA/W and low dark currents of <10 μA. Photocurrent generation is achieved by transitions from dopant-induced sub-bandgap trap states located ≈0.58 eV above the valence band to the conduction band, resulting in a peak detection wavelength of ≈2.3 μm. The wavelength of operation can be increased by choosing a dopant with an appropriate trap level, opening the possibility for on-chip detection throughout the mid-infrared.
Highlights
While a number of Si waveguide (SiWG) integrated optoelectronic devices have been demonstrated in this wavelength range[8, 9], efficient photodetection remains an important and challenging task
Spectral translation of mid-infrared signals to the telecom regime via four-wave mixing in SiWGs has been proposed for on-chip detection[10], which makes use of the sensitive integrated photodiodes (PDs) in the telecommunications wavelength range[11]
This method requires a high-powered pump laser and long, on-chip-waveguide lengths to achieve efficient wavelength conversion. Heterogeneous integration of both narrow-bandgap semiconductors[9,12,13,14] and graphene[15,16] with SiWGs has been demonstrated for on-chip mid-infrared detection
Summary
While a number of Si waveguide (SiWG) integrated optoelectronic devices have been demonstrated in this wavelength range[8, 9], efficient photodetection remains an important and challenging task. The responsivity, defined as R = Iph/Pin, where Iph is the photocurrent and Pin is the on-chip optical power entering the PD, is measured as a function of reverse bias voltage with 2.2 μm-wavelength excitation (Fig. 2c).
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