X-ray diffraction studies of microstructural transformations in single-crystal silicon during current filamentation

The (111) Bragg peak of p- and n-Si single crystals is studied when a large dc current (average current density 10 A/cm2) is passing through the specimen. The integrated intensity of the peak changed drastically with time after current filamentation, showing existence of microstructural transformations. The fresh samples (type A) showed a decrease in integrated intensity by a factor of about 50, 15 min after current filamentation, with a limiting current of 330 mA passing through the sample. The intensity partially recovered when the current was switched off, and, after cooling to room temperature, the specimen behaved differently when the electric field was again applied. The specimen (type B) then showed an increase in integrated intensity a couple of minutes after current filamentation so that the diffracted intensity became comparable to the type A specimen. Thereafter, with continued high current passing through the specimen, it behaved like a fresh silicon sample. The results are interpreted by considering formation of current filaments and consequent local heating.