C-V curves of several diodes of the BPW34 series and BXP61 type have been taken to characterize the thickness of the sensitive layer under reverse bias conditions. With about 8 V on the cathode, the typical sensitive layer thickness is about 50 um which corresponds well with the recorded energy spectra.

Based on the C-V curves, the following doping profiles are derived:

The effective charge carrier concentration 'Neff' is on average about half of the value reported in 2008 by Ravotti et al. which can be explained by manufacturing process variations. The similarity of the curve shapes confirms that all of the investigated diodes use either the same or at least very similar silicon chips. The regular micropattern visible in the doping profile curves is a measurement artifact that is caused by internal rounding errors of the C-V measurement device. The thin double lines indicate the error range of the instrument as stated by its manufacturer (Keysight B1500A with the MFCMU module).

In comparison to the BPW34F depletion plot in figure 5 (Ravotti 2008), the depletion plots shown here do not probe as well the shallow and deep ends of the depletion profile depth. This is caused by a smaller voltage range (25 V max. vs. ~180 V) and larger incremental step size (smaller step sizes would resolve the shallow depletion depths better) in the measurements above.

Further discussion of the CV measurements can be found in corresponding article.
The folder data_analysis_and_reference_measurements/diode_detector/diode_characterisation_and_simulation_plots provides the scripts to reproduce the corresponding plots. The raw C-V measurement data is available in data_analysis_and_reference_measurements/diode_detector/data/high_resolution_CV.