In situ trap parameter studies in CCDs for space applications

Charge-Coupled Devices are the detector of choice for the focal planes of many optical and X-ray space telescopes. In recent years, EM-CCDs, SCDs and CMOS sensors have been used, or baselined, for missions in which the detection of X-ray and visible photons are key to the science goals of the mission. When placed in orbit, silicon-based detectors will suffer radiation damage as a consequence of the harsh space radiation environment, creating traps in the silicon. The radiation-induced traps will capture and release signal electrons, effectively “smearing” the image. Without correction, this smearing of the image would have major consequences on the science goals of the missions. Fitting to observed results, through careful planning of observation strategies while the radiation dose received remains low in the early stages of the mission, has previously been used to correct against the radiation damage effects. As the science goals becoming increasingly demanding, however, the correction algorithms require greater accuracy and a more physical approach is required, removing the effects of the radiation damage by modelling the trap capture and release mechanisms to a high level of detail. The drive for increasingly accurate trap parameters has led to the development of new methods of characterisation of traps in the silicon, measuring the trap properties and their effects to the single-trap level in situ. Here, we summarise the latest developments in trap characterisation techniques for n-channel and p-channel devices.