Electrical Properties of Oxidized Si P-N Junctions

Abstract

The effects of various oxidation methods on the stabilization of the Si surface are discussed. From the temperature dependence of reverse current, the energy level of the surface trapping centers in thermally oxidized Si p-n junctions is obtained as a range of 0.2 to 0.3 eV from either conduction or valence band. The n-type conversion on p-type surface due to thermal oxidation which may perhaps correspond to this new level plays important undesirable roles in its stability. On the converted surface of the oxidized Si p-n junctions, although surface breakdown voltage V _s approaches on a net bulk breakdown voltage V _B , the generation of 1/f noise becomes unsatisfactorily predominant. It has been, however, proved that the current fluctuation due to charge transfer between the bulk Si and the slow state is sufficiently avoidable by thick oxide fllm. According to the measurements of reverse current I _r and photoresponse, the n-type conversion layer disappears after γ ray irradiation from Co⁶⁰ and reappears after annealing: another new level may be formed by γ ray. Furthermore, it has been found that the 1/f noise generated through the oxide fllm in M-O-S (Metal-Oxide-Si) diode is directly proportional to nearly the square of total current I _r which is not the case in usual p-n junction.