Charge collection and SEU sensitivity for Ga/As bipolar devices

Charge collection was measured across the base-emitter heterojunction to test certain assumptions of the standard sensitive-volume models for calculating SEU (single-event-upset) rates. The observed dependence of charge collection on the LET (linear energy transfer) and the angle of incidence of 4.4-MeV on oxygen ions is consistent with the hypothesis that the charge collected equals the product of LET and path length through a sensitive volume of fixed dimensions. The data suggest that the switch from MBE (molecular beam epitaxy) to MOCVD (metal-organic chemical vapor deposition) processing resulted in an increase in the thickness of the sensitive volume from 0.11 to 0.25 mu m.<
>