Modeling of Columnar Recombination for High-Energy Photon Generated Electrons and Holes in Amorphous Selenium

An analytical model is developed to study the mechanisms of X-ray generated free Electron–hole pair (EHP) creation energy in amorphous selenium (a-Se) at high electric fields. The model is presented to show the electric field and temperature dependence of the charge extraction yield limited by the columnar recombination for the materials that have widely unequal drift mobility for electrons and holes, such as a-Se. The model is compared with Jaffe’s columnar recombination model with widely varying field and temperature. In addition, the free EHP creation energy is calculated by incorporating the initial charge extraction yield and the charge collection efficacy of the free carriers. Also, the results of this model are compared with the recently published experimental results on EHP creation energy. The analysis of the results confirm that the proposed model gives the best possible explanation to the columnar recombination mechanisms in a-Se and the free EHP creation mechanisms at diagnostic X-ray exposures can be described by the columnar recombination.