AbstractID: 6535 Title: Mechanism for charge creation in a-Se based x-ray
detectors
X-ray detectors based on the photoconductor amorphous selenium (a-Se) are
under study in medical imaging for diagnostic purposes and for the verification of
radiotherapy treatments. Although a-Se has been studied for medical imaging since the
1970s, the mechanism of charge creation and recombination is poorly understood. This
problem is addressed in this work by developing a quantitative theory which includes
collective and single electron-hole pair excitations by the passing electron. The theory is
incorporated into a Monte Carlo code to calculate track structures in a-Se. The initial
positions of the electron-hole pairs along the track structures are used to study the amount
of recombination versus incident x-ray energy and applied electric field. The
experimentally observed energy dependence of recombination is attributed to a spur size
which is dependent on the velocity of ionizing electrons. Our theory and simulations
agree with available experimental data in the energy range from 20 keV to 10 MeV. The
theory presented in this work can be viewed as an extension to the Onsager single
electron-hole pair recombination model to include a mechanism for multiple electronhole pair creation in a spur.