A model of charge collection process in a silicon surface barrier detector

Silicon surface barrier detectors have been widely used for the detection of charged particles. This type of detector has a timing feature called plasma time, which is defined as the time interval from 10% to 90% of the pulse height. It causes time jitters and affects the trigger timing of the electronic circuits. The plasma time reflects the movement of electrons and holes as well as the charge collection process inside the detector. The present study discusses the charge collection process in relation to the Ramo's theory, according to which a pair of an electron and a hole between parallel electrodes induces a charge as it moves through a distance. The top and bottom positions of a plasma column is calculated assuming that the column is in the form of a cylinder with uniform electron and hole densities. An equation is also proposed for the time and position where the plasma column disappears. Induced current is then calculated based on the Ramo's theory. The induced charge is obtained as a time integral of the induced current. The induced current is discussed separately for the current induced by carriers outside the plasma column and that inside it. (N.K.)