Deep Level Behaviour in Superlattice
In the old times there were two kinds of physicists working on semiconductors, the ones who were studying the behaviour of electrons in the bands and the other ones who were growing materials and making devices with them. One day, the second ones realized that, if their devices did not work, this was because a kind of physics had been forgotten, the physics of defects, and that it is also important to know the behaviour of electrons when they are localized inside the forbidden gap. It seems that, with the advent of heterostructures and superlattices, the same process starts again: some play with electrons in fancy band structures while others tailor new materials which are supposed to have the virtue of making working devices. However, the question of the influence of defects will arise soon. For instance, those who hope to replace a layer containing defects, such as DX centers in GaAlAs, by a GaAs-GaAlAs superlattice should fear that this superlattice could contain even more defects than a simple GaAlAs layer. There is indeed apparently no transient phenomenum associated with charge trapping on the DX centers in such superlattices, but there are other types of transients (see fig. 1) probably due to a broad continuum of electron states, originating presumably from defects at the interfaces (1).
KeywordsCharge State Deep Level Transient Spectroscopy Super Lattice Energy Level Position Configuration Coordinate Diagram
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