Angular Dependence of Charge Funneling in Si and GaAs Devices

Charge collection and transient current measurements on n-type GaAs and Si Schottky diodes bombarded with single alpha particles reveal a strong dependence on angle of incidence. Prompt recombination is evident in both materials. The magnitude of charge collected by funneling is proportional to the charge generated in the depletion region. An alternative interpretation of the data is that charge generated to a certain depth below the junction, proportional to the depletion width, is collected by funneling. The increased collection of charge with increasing angle appears to be due to a longer collection time. These measurements indicate that dynamic processes occur during charge funneling which are not fully described by existing phenomenological models.