Table 8‑2: Definition of displacement damage effects

Parameter	Phenomenology and observation	Technologies affected
Charge-transfer efficiency (CTE)	Creation of traps in active volume of CCD – reduced charge collection from each pixel, also streaking observed due to the delayed release of trapped charge.	CCD
Dark current	Excess charge from electro-optic sensor due to charge collection from radiation-induced defects.	CCD APS photo-diodes photo-transistors
Hot spots	Defect-induced charge generation in specific pixels which become brighter than the average dark current. These are usually defined in the context of the application and identified by the image-processing software as “bad pixels”. Very bright spots can result from field-enhanced emission mechanisms.	CCD APS
Random telegraph signals (RTS)	Two or more multi-level dark-current states with random switching between the dark current states from seconds (for imager at room temperature) to hours (if operated at reduced temperatures)	CCD APS
Bright columns	Defect-induced dark current can saturate a pixel with a time-constant comparable to or longer than device read-out times. Information from one or more pixels after the damaged pixel are thus rendered unreadable.	CCD
Reduced photo-current / Pixel responsivity	Reduced charge collection as a result of decreased minority carrier life-times	APS photo-diodes photo-transistors
Threshold current
Light output	Increase in charge traps result in greater non-radiative recombination of electron-hole pairs and hence reduced radiation power efficiency	LED laser diodes
hFE	Reduced minority carrier life-times in BJT base result in lower currents between the collector and emitter, and hence reduced transistor gain.	BJT
Open-circuit voltage	The open circuit voltage is reduced by introduction of recombination centres in the depletion region which increase the dark current.	Solar cell
Short-circuit current	Recombination centres reduce minority carrier life-time in the neutral regions of the device resulting in reduced quantum efficiency (i.e. reduced charge collection).	Solar cell
Power output	See open circuit voltage and short circuit current.	Solar cell
Energy calibration Detector resolution	Reduced charge collection efficiency (CCE) results in less signal from detector per unit energy deposition, and greater statistical errors in the signal (hence reduced resolution). For cryogenic detectors, these parameters show complex behaviour with changes in temperature.	Semiconductor radiation detectors