Simulation by Monte Carlo of the X ray Transport in PIN Type a-Si:H Radiation Detectors

Low energy X rays usually employed in mammography, were transported in hydrogenated amorphous silicon PIN diodes using MCNP-4C system code based on Monte Carlo simulation. The deposited energy distribution in these devices, useful as radiation detectors in medical imaging applications, was evaluated for 7-50 μm thick intrinsic layers. The energy spectrum in different depths of the intrinsic layer shows a lineal increase of the deposited energy, and near the metal electrodes this increase is significantly higher by an order of magnitude. The influence of the material and geometry of the top electrode on the energy deposited inside the intrinsic layer, as well as the effect of the addition of the passivation layer are analysed in the text