A charge collection study with dedicated RD50 charge multiplication sensors

This study investigates the charge collection efficiency of silicon strip detectors, produced by MICRON Semiconductor Co., Ltd. within the CERN RD50 collaboration, designed specifically to understand the effect of design parameters on the onset and magnitude of charge multiplication. Charge collection measurements are performed before and after irradiation with a proton fluence of $1 \times 10^{15} \ 1 \ \rm{MeV} \ \rm{n}_{eq}/cm^2$ ($\rm{n}_{eq}/cm^2$) and neutron fluence ranging from $1 – 5 \times 10^{15} \rm{n}_{eq}/cm^2$. Structures on these devices include varying diffusion times and energies for the implantation process, different sensor thicknesses, the use of intermediate biased or floating strips between the readout strips, and several different strip width and pitch geometries. The charge collection for these devices is studied as a function of the bias voltage, looking for indications of charge multiplication. Results are compared to standard float zone 300 $\mu \rm{m}$ thick silicon strip sensors having a strip width of 25 $\mu \rm{m}$ and pitch of 80 $\mu \rm{m}$.