Abstract
Metal-semiconductor-metal Si waveguide photodetectors are demonstrated with responsivities of greater than 0.5 A/W at a wavelength of 1550 nm for a device length of 1mm. Sub-bandgap absorption in the Si waveguide is achieved by creating divacancy lattice defects via Si(+) ion implantation. The modal absorption coefficient of the ion-implanted Si waveguide is measured to be ≈ 185 dB/cm, resulting in a detector responsivity of ≈ 0.51 A/W at a 50 V bias. The frequency response of a typical 1mm-length detector is measured to be 2.6 GHz, with simulations showing that a frequency response of 9.8 GHz is achievable with an optimized contact configuration and bias voltage of 15 V. Due to the ease with which these devices can be fabricated, and their potential for high performance, these detectors are suitable for various applications in Si-based photonic integrated circuits.
Highlights
Ion-implanted Si waveguide photodetectors (PDs) have recently been incorporated into numerous photonic integrated circuits and systems [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
By applying a bias across the Schottky contacts, carriers generated in the semiconductor region are swept out to the contacts while the barrier height prevents current across the device, unlike internal photoemission devices where carriers are excited over the barrier to generate photocurrent [19]
Previous MSM waveguide PDs based on Ge [17] or InGaAs [18] utilized Schottky contacts directly on top of the waveguide allowing for low operating voltage and high frequency response
Summary
Ion-implanted Si waveguide photodetectors (PDs) have recently been incorporated into numerous photonic integrated circuits and systems [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. Multiple configurations have been used to enhance detector responsivity, including resonant-cavity-enhanced detectors [4] and avalanche-multiplication detectors [5,6] These ion-implanted waveguide PDs have been incorporated in Si photonic devices for power monitoring [11], wavelength monitoring [12], thermal tuning [13], and variable optical attenuation [14]. The majority of these devices are based on reverse biased p-i-n rib waveguide diodes, similar to the structure shown in the bottom inset of Fig. 1(a). Upper inset giving the cross-section of our MSM structure. (b) SEM image of 250 μm device
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