W-center LED
============
Description
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W-centers are emissive centers in silicon produced by ion bombardment. By putting them in a PN junction in a waveguide, the W-centers can be excited electrically. This is the principle underlying the waveguide-coupled all-silicon light-emitting diode (LED) developed in :cite:`Buckley:17`.

.. image:: layout_pics/led_blender.png
    :width: 70%


Characteristics
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The light-current (LI) and current-voltage (IV) curves of a previous LED are pictured here. Optical intensity is measured in clicks per second from an on-chip single photon detector.

.. image:: data/led_IV.pdf
    :width: 45%
.. image:: data/led_LI.pdf
    :width: 45%

The W-centers emit around 1220nm. The spectrum of the emitted light under different biasing conditions is shown here

.. image:: data/led_spectrum.pdf
    :width: 50%


Layout
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.. todo::

    Need to work out the standard values, make a python file, then make a GDS...