Unexpected increase in the thermal generation rate of bulk GaAs due to electron-beam metallization

It is demonstrated that the thermal generation rate in the bulk depletion regions of GaAs p-n junctions can be as much as three-orders-of-magnitude greater for samples metallized in e-beam evaporators as compared to thermal evaporators. This degradation is unexpected because the low-energy radiation present in such e-beam evaporation systems is unable by itself to cause atomic displacement responsible for defect creation in GaAs. Results derived from samples metallized in the e-beam evaporator indicate, however, that low-energy electrons are somehow involved in the formation of the defects responsible for the increased generation rate. Experiments performed in controlled-radiation environments have clearly demonstrated that neither simple radiation damage from electrons or from x-rays is sufficient to degrade these GaAs devices. Likewise, the simple diffusion of impurity ions in the absence of a high fluence of low-energy electrons is also insufficient. Therefore, the experimental results suggest a damaging mechanism in which the presence of both low-energy electrons and impurity ions is necessary to cause the increase in generation rates observed in bulk GaAs