Electrical Properties

Abstract

The MOS system in the form of a Si substrate with a thermally grown SiO2 layer and a metal gate is one of the best investigated material systems worldwide with early investigations dating back to the 1950s. The knowledge about this material system was extended in the 1960s and 1970s, and later developments perfected the picture with ultrathin SiO2 layers, MNOS devices and the introduction of high-kdielectrics. There are a couple of extended and excellent surveys dealing with both the fundamentals of semiconductor physics and the advanced investigation techniques developed and refined over decades, for example, [194–196]. Therefore, it is assumed within the frame of this book that the basic concepts of semiconductor physics like the bandgap model or doping are known, and advanced methods will only be treated in detail as far as they are needed for the understanding of the physical background. Consequently, Sect. 3.1 briefly reviews what is known about the charge injection and transport in MOS devices with respect to the specific structure we have used. Whereas the electrical properties of unimplanted and RE-implanted MOSLEDs in the as-fabricated state are discussed in Sect. 3.2, Sect. 3.3 focuses on these devices under constant current injection. Based on these results, a more general model of the electrical charge trapping behaviour is outlined in Sect. 3.4.