Table 1.
Characteristics of different components of the stimulation artifact on μLED optoelectrodes.
| Type | Source | Magnitude | Shape (polarity) | Location dependence | Suppression scheme |
|---|---|---|---|---|---|
| EMI | n-GaN | Several mVs (combined with EMI from LED interconnects) | ^-shaped (positive, or concave down) | No | Shielding layer |
| EMI | LED interconnects | Several mVs (combined with EMI from n-GaN) | ^-shaped (positive, or concave down) | Yes | Shielding layer and transient pulse shaping |
| EMI | LED | Up to several 102 μVs | ^-shaped (positive, or concave down) | Yes | Transient pulse shaping |
| PV | Silicon substrate | Up to several 102 μVs | v-shaped (negative, or concave up) | No | Substrate doping |
The magnitude of each stimulation artifact component was derived from the calculated difference in the magnitudes of the stimulation artifact measured from devices that did and did not utilize the suppression scheme indicated. The measurement of the stimulation artifact magnitude was made with μLED irradiance of 75 mW mm–2. The shape of the stimulation artifact indicates the shape observed in the recorded signal at the onset of the optical stimulation.