Analysis of the transient response of LED-illuminated diodes under heavy radiation damage

The changes of the electrical properties induced by hadron irradiation on s ilicon detectors have been studied by using the device level simulator HFIE LDS. The model of the radiation damage assumes the introduction of radiatio n-induced acceptor and donor "deep-levels". The electric field profile and the space charge region extension have been calculated for differently irra diated structures The simulation has been carried out at different biases i n order to study the evolution of the space charge region of irradiated det ectors as a function of the applied voltages, below and above the full depl etion. The time-dependent current responses and the charge collection prope rties of the structure illuminated by a red LED light have been calculated. The use of the red light results in a shallow (quasi-surface) generation o f e-h pairs in silicon, which has been properly taken into account by the s imulation. The results of the simulations have been compared to experimenta l measurements carried out at CERN on samples irradiated with 24 GeV/c prot ons. The comparison results in a satisfactory agreement, and supports the p hysical interpretation of experimental data. (C) 2000 Elsevier Science B.V. All rights reserved.