Transient Photocurrents in SOS Structures

Silicon-on-Sapphire (SOS) construction reduces junction photocurrents to such low levels that other radiation-induced currents tend to dominate the response of an SOS circuit to transient ionizing radiation. The results of experiments and calculations suggest that photoconduction of the sapphire substrate accounts for most of the observed "excess" currents internal to these circuits - while gas ionization effects are significant at the external device terminals.