Parallel biased GaAs photoconductive detectort

摘要

The response of a transverse biased photoconductive detector (PCD) may be modeled as a continuously variable parallel resistor through the depth of the detector. Since the bias is perpendicular to the dose gradient the electric field is constant and the mean conductivity is proportional to the mean dose rate. The response of a parallel biased PCD can be modeled as a continuously variable series resistor through the depth of the detector with the bias electric field dependent on the resistivity at the given depth in the detector. Hence, even though the front region the PCD becomes highly conductive, the PCD will not respond unless free carriers are generated through the entire depth of the PCD between the bias electrodes. Experimental measurements on parallel biased gallium arsenide, GaAs, PCDs using the MBS (Modular Bremsstrahlung Source) pulse x-ray source at AEDC (Arnold Engineering Development Center) are given that substantiate the response model. Agreement in the response between PCDs of varying x-ray filtration were observed with the effective dose model given in the paper as opposed to a 40% discrepancy when the mean dose is used.