Study of CMOS/SOS technology photocurrents

The authors present the results of experiments and simulations performed on CMOS/SOS (silicon on sapphire) technology band systems exposed to transient irradiation. They describe some sapphire behaviors arising from the presence of a space charge zone which limits photocurrent. The band array developed for the sapphire photocurrent study revealed particular characteristics: memory effect, characteristic waveform, and constant amplitude for inter-band spacings up to a few tens of microns. The particular characteristics of sapphire photocurrent imply that certain precautions must be taken when designing test patterns and performing tests. Simulation under a flash revealed the creation of a space charge zone which could explain most of the characteristics observed. This study shows the benefit of using a software package such as ACCES for simulating photocurrents in insulating materials