Carrier drift and diffusion characteristics of Si particle detectors measuredin situduring 8 MeV proton irradiation

Abstract

The carrier drift and recombination parameters determine the functional characteristics of Si high energy particle detectors. In this work, techniques for the in situ control of drift-diffusion current transients during 8 MeV proton irradiation are discussed. The characteristics obtained in silicon particle detectors and carrier drift-diffusion and generation parameters variations during proton exposure are analysed. The models of current transients within a depleted diode with the drifting-induced charge domain at low and high densities of light excited excess carriers within the diode base region have been proposed. A small impact of radiation defects on carrier drift/diffusion parameters and more complex variations of excess carrier recombination / trapping lifetimes during irradiation have been revealed.

Currents Induced by Injected Charge in Junction Detectors

“…The electrical ( U r = 150V) and optical ( n ex0 ) parameters were carefully controlled to be fixed within measurements. The sample was kept in air just behind the neutron beam cone, while other experiment details are published in [ 14 , 28 ]. Evolution of the current transients is illustrated in Figure 5b , where currents had been controlled starting from that registered in the non-irradiated diode up to exposure duration for which the collected irradiation fluence reaches value of > 10 14 n/cm 2 .…”

“…This regime is partially discussed in [ 14 ]. Let's consider a regime of the applied reverse voltages U bi < U < U FD on the n-type conductivity layer at an assumption that the electron domain is injected nearby the metallurgic abrupt junction, and the strength of the electric field there is capable to separate the electron-hole pairs, with consequent extraction of holes into p + -type layer.…”

“…Using the methodology described in [ 14 ], an instantaneous field distribution is obtained by integrating the first Poisson equation and by assuming an infinitesimally thin drifting domain of surface charge of density q e , as: …”

“…A few aspects of the impact of carrier trapping on the injected charge transients for a partially depleted junction layer have been mentioned in [ 14 , 18 ]. Evaluation of other parameters (e.g., t dr ) of the transients determined by the injected charge drift and trapping becomes even more complicated, and it can be implemented only by the numerical methods.…”