Novel method for identifying the cause of inherent ageing in Electron Multiplying Charge Coupled Devices

The charge multiplication process used in the Electron Multiplying CCD (EMCCD) is subject to an ageing effect in which the gain achieved at particular avalanche potentials, gradually decreases during operation. To utilise these devices for both space and terrestrial applications where recalibration of the gain is not feasible, a comprehensive understanding of the ageing process is required. A custom automated test equipment (ATE) has been produced and used to develop the techniques required for investigating the ageing process alongside the verification of simulation work on the subject. Simulation work carried out by e2v technologies has suggested hole build-up at the Si/Si0₂ interface below one of the transfer gates. This build up of holes has now been linked with a reduction in avalanche potential in the device. A novel experimental technique has therefore been developed to determine the actual potentials within the device and thereby determine the validity of this prediction.The initial results tend to support simulation as an increase in the potential beneath one of the phases is observed.