Influence of non-equilibrium carriers on the surface breakdown of diodes and MOS-structures

The effect of a reduction of breakdown voltage
\Delta V_{B}
by external illumination of an oxide protected planar n
⁺
p diode or by non-equilibrium carriers drifting in a surface channel has been investigated. The appearance of a localized area where the external light spot causes maximum
\Delta V_{B}
is described. The influence of light wavelength and ambient has been studied. A model is presented to explain the facts that a small current of non-equilibrium carriers controls an avalanche current which is several orders of magnitude larger, and that no lock-on mechanism has been observed. The model involves the field enhancement by slowly moving carriers in the space charge region at a narrow distance from the Si-SiO
2
interface. The influence of surface potentials on these carriers is emphasized.