Response of amorphous silicon p-i-n detectors to ionizing particles

Prototypes of thin film p-i-n amorphous silicon detectors, having intrinsic layer thicknesses ranging from 3 to 18 μm, were designed and fabricated, and their response to protons of 1.3 to 11.6 MeV, and to α particles of 1.6 to 14.6 MeV was studied. The collection efficiency of the charges generated by a particle is found to decrease sharply with increasing dE/dx, for dE/dx values greater than 10 keV/μm. However, there exists a domain of oblique angles of incidence, relatively high applied biases and low dE/dx values over which the signal amplitude varies linearly with energy loss. Pulse shape studies show the signal to consist of a steep leading edge, attributed to prompt electron collection, and a slow component showing evidence of multiple-trapping transport of holes, which is a possible cause for incomplete collection of the generated charge at the maximum attainable field of 60 V/μm. Finally, all detectors give signal amplitudes compatible with a mean electron-hole pair creation energy of 3.4 to 4.4 eV in a-Si:H. (orig.)