RESPONSE FUNCTIONS OF A SI(LI) DETECTOR FOR PHOTON ENERGIES FROM 1 TO 10 KEV

We report the effect of incomplete carrier collection on response functions of a Si(Li) detector for photon energies from 1 to 10 keV. We calculate carrier collection probability as a function of generated carrier position using a simple model including drift, diffusion, and reflection at the gold-silicon interface. We simulate the energy loss of secondary electrons generated by photoabsorption in the silicon and the gold contact using a Monte Carlo method. Calculated response functions agreed well with measured ones over the entire energy range. We explain the threshold of the low-energy tail, observed for photon energies just above the Si K absorption edge, using a carrier reflection model. We also explain the flat continuum by secondary electrons escaping from the silicon to the gold contact and penetrating the silicon from the gold contact.