Ionizing Radiation Detector

A single-photon avalanche diode (SPAD) array for an ionizing radiation detector comprising:

• a first common semiconductor substrate;
• a first plurality of SPAD microcell structures disposed at a top face of the first common semiconductor substrate, each SPAD microcell structure of the first plurality of SPAD microcell structures comprising a first semiconductor junction that is reverse-biased beyond a first breakdown threshold for the first semiconductor junction;
• a common anode connection and a common cathode connection to each of the SPAD microcell structure of the first plurality of SPAD microcell structures and configured to operate as an output for the SPAD array;
• wherein charge drift within the first common semiconductor substrate is not inhibited from exciting more than one of the SPAD microcell structures of the first plurality of SPAD microcell structures by isolation barriers.

A method comprising:

• controlling biasing of a first plurality of single-photon avalanche diode (SPAD) microcell structures disposed at a top face of a first common semiconductor substrate of an ionizing radiation detector, each SPAD microcell structure of the first plurality of SPAD microcell structures comprising a first semiconductor junction that is reverse-biased beyond a first breakdown threshold for the first semiconductor junction;
• receiving ionizing radiation at the ionizing radiation detector;
• permitting charge drift within a first common semiconductor substrate in response to receipt of ionizing radiation to excite one or more of the SPAD microcell structures of a first plurality of SPAD microcell structures, wherein the charge drift is not inhibited from exciting more than one of SPAD microcell structures of a first plurality of SPAD microcell structures by isolation barriers;
• and
• measuring electrical characteristics of a signal provided on an output, the output being a common anode connection and a common cathode connection to each of the SPAD microcell structures of the first plurality of SPAD microcell structures.