A process and deep level evaluation tool: afterpulsing in avalanche junctions

A technique for a separate experimental characterization of generation centres and deep levels in junctions is presented. The test device required is a small junction that operates in Geiger-mode above the breakdown level. Time-resolved measurements of correlated afterpulsing effects are exploited for separating noise contributions due to generation centres and to carrier trapping in deep levels. Release transients down to the nanosecond range are characterised and lifetimes of individual trap levels are measured. Experimental data for devices fabricated with different technologies illustrate the information gained about the efficiency of the fabrication process and in particular of gettering steps.