 Solution

A fast charged particle loses energy by ionizing and exciting silicon, creating electron–hole pairs along its path. In a reverse-biased microstrip diode, the electric field separates and drifts the electrons and holes toward opposite electrodes. Their motion induces a current on the strips, which is integrated by the readout electronics to locate the hit.

The bias depletes the bulk of mobile equilibrium carriers, reducing conduction and capacitance, and supplies rapid directed charge collection before recombination or trapping. Without a collecting field, diffusion is slow and charge spreads or recombines, degrading signal and position measurement. The signal is generated by the traversing particle's energy deposition, not by the bias creating the ionization charge.