Charge collection response of SI GaAs p-i-n detectors

The charge collection response of semi insulating GaAs p-i-n detectors to alpha particles has been measured and compared to the results of a simple charge carrier drift model. The model uses an electric field distribution which has been measured using a surface probe technique and assumes that the drift lifetimes are independent of the electric field strength. By comparing the simulated data with the experimentally measured charge collection efficiency, mean drift lifetimes have been deduced of 0.5 ns and 20 ns for the electrons and holes respectively. The model has also been used to simulate the charge collection response of GaAs detectors to gamma rays and to minimum ionising particles