The results of experimental studies of the electrical parameters and surface morphology of GaAs structures of ring and circular Schottky diodes before and after irradiation with ~ 1 MeV neutrons are presented. Bulk radiation defects were revealed by atomic force microscopy (AFM). Based on the results of capacitance-voltage measurements, the concentration of electrons was determined and their mobility was estimated before and after irradiation. On the basis of the results obtained using a combination of these methods, a technique is proposed for determining the average sizes of the space charge regions of clusters of radiation defects.