Vertical gate guard ring for single photon avalanche diode pitch minimization

A photon sensing system, comprising:

• a photon detection array having a plurality of photon detection devices, wherein each one of the photon detection devices includes:
• a single photon avalanche diode (SPAD) disposed in a first region of a first semiconductor layer, wherein the SPAD includes a multiplication junction defined at an interface between an n doped layer and a p doped layer of the SPAD in the first region of the first semiconductor layer;
• a vertical gate structure disposed in the first semiconductor layer proximate to the SPAD, wherein the vertical gate structure surrounds the SPAD to isolate the SPAD in the first region of the first semiconductor layer from a second region of the first semiconductor layer on an opposite side of the vertical gate structure, wherein the n doped layer and the p doped layer of the SPAD laterally extend within the first region of the first semiconductor layer to contact the vertical gate structure;
• and
• a depletion layer generated around a perimeter of the SPAD at an interface of the vertical gate structure and the p doped layer in response to a gate bias voltage coupled to the vertical gate structure, wherein the depletion layer isolates the SPAD from the second region of the first semiconductor layer on the opposite side of the vertical gate structure;
• and
• support circuitry coupled to the photon detection array to support operation of the photon detection array, wherein the support circuitry is disposed in a second semiconductor layer.