MSM waveguide detector for silicon photonics simplifies manufacture

May 1, 2014
The ion-implanted silicon (Si) waveguide detector is commonly used as an integrated light detector in photonic integrated circuits; however, these detectors require numerous masking and alignment steps in their manufacture and in addition have a relatively high junction capacitance.

The ion-implanted silicon (Si) waveguide detector is commonly used as an integrated light detector in photonic integrated circuits; however, these detectors require numerous masking and alignment steps in their manufacture and in addition have a relatively high junction capacitance. A team of scientists from Columbia University (New York, NY), Brookhaven National Laboratory (Upton, NY), and the State University of New York at Albany have fabricated versions of these waveguide detectors that have a metal-semiconductor-metal (MSM) structure, simplifying manufacture and lowering junction capacitance. Commonly used in larger planar detectors, the MSM approach relies on paired Schottky barriers with titanium/gold (Ti/Au) contacts rather than a reversed-bias p-i-n junction.

The 1-mm-long monolithic device, which is fabricated in a rib waveguide, has a responsivity of 0.51 A/W at a 50 V bias and a frequency response of 2.6 GHz, with simulations showing that tweaks to the device could push the frequency response up to 10 GHz or higher at a bias voltage of around 15 V. Based on the average absorption coefficient of 185 dB/cm, the calculated quantum efficiency of the MSM detector is 42%. The device could be made CMOS compatible by using copper rather than Ti/Au for the Schottky contacts.

Contact Brian Souhan at[email protected].

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