Charge collection efficiency study of silicon microstrip sensors

The charge collection efficiencies (CCEs) of various AC-coupled single-sided silicon microstrip sensors were measured to find an optimal sensor design for different readout methods. A 820 nm wavelength pulsed laser was used as a light generation source to study the responses of the prototype microstrip sensors. Five different microstrip sensors of two types (A and B) were designed for this purpose and were fabricated on high resistivity and n-type silicon wafers. The readout pads in types A and B were located inside and outside the guard ring surrounding the active sensor area, respectively. The sensors at an operating voltage of 80 V were irradiated by using a pulsed laser, producing ~22000 electron-hole pairs per pulse. The signals, ADC counts, were measured by moving the sensors while maintaining the laser in a fixed position. The CCEs for 10 different microstrip sensors were calculated from the maximum and the minimum ADC counts in each designed microstrip sensor. This study showed that the hit-position dependences of the signals and the CCEs for the three different readout methods were well evaluated by using a pulsed laser without using charged particles from accelerators.