A Near-Infrared Enhanced Silicon Single-Photon Avalanche Diode With a Spherically Uniform Electric Field Peak

A near-infrared (NIR) enhanced silicon single-photon avalanche diode (SPAD) fabricated in a customized
$0.13~\mu \text{m}$
CMOS technology is presented. The SPAD has a depleted absorption volume of approximately
$15\,\,\mu \text{m}\,\,\times 15\,\,\mu \text{m}\,\,\times 18\,\,\mu \text{m}$
. Electrons generated in the absorption region are efficiently transported by drift to a central active avalanche region with a diameter of
$2~\mu \text{m}$
. At the operating voltage, the active region contains a spherically uniform field peak, enabling the multiplication of electrons originating from all corners of the device. The advantages of the SPAD architecture include high NIR photon detection efficiency (PDE), drift-based transport, low afterpulsing, and compatibility with an integrated CMOS readout. A front-side illuminated device is fabricated and characterized. The SPAD has a PDE of 13% at wavelength 905 nm, an afterpulsing probability < 0.1% for a dead time of 13 ns, and a median dark count rate (DCR) of 840 Hz at room temperature. The device shows promising performance for time-of-flight applications that benefit from uniform NIR-sensitive SPAD arrays.