Time performances of a scintillator-photodiode system

Time characteristics of the system with surface-barrier photodiode are investigated by calculations on the example of photodiodes made of semiconductor with electron conductivity. The forms of charge pulses of scintillator-surface-barrier photodiode system are obtained at different values of the relation of scintillator luminescence time constant to the time of electron flight and holes. It is shown, that the charge pulse form of the system with surface-barrier photodiode is determined by silicon specific resistance and the constant of the scintillator luminescence time. The pulse form also depends on the diode side, where scintillator optical coupling is carried out: either from the side of golden contact or back contact side. The time of charge pulse increasing is determined by luminescence time for great constants of the scintillator luminescence time. Besides, an essential difference is observed in the time of pulse increasing in the case of generating nonequilibrium carriers by photons of scintillations and in the case of uniform generation by the depth of sensitive region. It is noted, that during generating the current carriers from the side of back contact a time delay from generation moment up to the moment of pulse occurrence, is observed. It is explained by the fact, that nonequilibrium carriers are generated in this case in the region of weak field intensity, and therefore the rate of their movement is inessential. The value of the potential slightly changes with the coordinate change in this region, i.e. the charge on a collecting electrode is not practically guided up to a certain moment of time during the movement of nonequilibrium carriers