A low-cost small-size commercial PIN photodiode: II. Comparison of measurements with monoenergetic electrons to analytical expressions and Monte Carlo simulations

Commercial PIN photodiodes, repurposed as particle detectors, have received a lot of attention along the past

decades because they can offer a low-cost solution suitable for several applications. The BPX-65 photodiode has

been chosen because of its interesting features for measuring electrons in a harsh radiation environment close to

the beam of an accelerator. Its electrical characterisation and its application to photon spectrometry have been

presented in the companion paper I. Here, its response function (RF) to electrons is investigated using the beam

from an electron accelerator with a small energy spread. The empirical expressions for the RF available in the

literature have been improved, simplified, and combined to obtain a final form with 7 free parameters: 4 nonlinear

and 3 linear. A special fitting procedure, which takes advantage of the presence of the linear parameters,

is described. The behaviour of these parameters with beam energy and bias is investigated to uncover the

physical origin of the three components included in the proposed RF. The interpretation of the features of the

spectra is confirmed by Monte Carlo simulations carried out employing the general-purpose PENELOPE/penEasy

package. To take into account the charge-collection properties of the device, a simple model has been implemented

and is compared to data. It has then been possible to estimate the thickness of the partially dead layer

from the experiment.