Electrical-modelling, design and simulation of cumulativeradiation effects in semiconductor pixels detectors: prospects and limits

Abstract

Silicon detectors have gained in popularity since siliconbecame a widely used electronic semiconductor material. Silicon detectorsare used in particle physics as well as imagers for pixel based detectingsystems. Over the past twenty years a lot of experimental efforts have beenfocused on the effects of ionizing and non-ionizing radiation on siliconbased detectors including charged coupled devices (CCDs). Some of thisresearch was performed in the framework of high luminosity particle physicsexperiments, along with radiation hardness studies of basic semiconductorsdevices. The building blocks of silicon pixel detectors including CCDs aresimple PIN or PN structures partially or totally depleted, or even MOS andAPD (Avalanche PhotoDiode) structures. Bulk or surface defects considerablyaffect the transport of free carriers. We propose here guidelines for pixeldesign. The method takes into account the properties of defects and will betested through two pixel structures. The electrical properties of defectscan be reduced to basic parameters, which can be introduced in a standardsimulation code to make predictive simulations. We include an analyticalmodel for defect build up derived from isochronal annealing experiments.Studying pixels detectors with different geometrical structures andfabricated with various semiconducting materials is made possible with thismethod. Its purpose is to provide an alternative to tedious and extensiveradiation tests on fabricated detectors. Predicting the pixel behaviourw.r.t. defect properties is necessary for the long-term reliability ofdetectors and for making them radiation hard. A general method for pixeldesign is introduced and we will show how it can be used for the design ofalternative (germanium) pixels.