Field-assisted Diffusion Research Articles

Carrier-collection efficiencies in amorphous hydrogenated silicon Schottky-barrier solar cells

We report the results of a systematic study of correlations in the collection efficiency, collection length, depletion width, midgap density of states and energy-band gap in sputter and silane-decomposition-produced amorphous hydrogenated silicon Schottky diodes. Films produced by sputtering have a collection length Lc, which is less than the depletion width W, unlike silane-decomposition-produced films for which Lc≃W. We show that the relatively weak variation of the deduced hole-mobility-lifetime product with midgap state density and temperature is consistent with the holes becoming immobilized before recombining. The collection efficiency is found to be controlled dominantly by the field-assisted diffusion of carriers in the depletion region, and not limited by geminate recombination.

Memory Switching and Crystallization in Selenium

A memory switching effect in bulk polycrystalline selenium has been investigated. I–V characteristics are related to structural changes revealed by microscopic examination, where it is shown that the switching mechanism is a crystal–amorphous phase transformation.A molten zone, produced by a direct current through the sample, undergoes a polarity dependent motion. The zone motion is discussed in terms of field-assisted ionic diffusion and it is suggested that this could be made into a useful crystal growing technique.