ABSTRACT
For nearly 20 years, the absence of electronic diffusion [1] in two dimensional systems for temperatures approaching zero was commonly accepted, with the coherent single electron backscattering being the origin of that effect. Thus the claim for a metal-to-insulator transition in high-mobility Si-metal oxide semiconductor (MOS) structures in 1994/95 [2] was met with great scepticism. It was quite important that the finding was confirmed for Si-MOS samples from a different source [3] and consecutively also for p-type Si/SiGe [4], n-Si/SiGe [5,6], p-AlGaAs [7], n-AlGaAs [8] and n-AlAs [9] structures.
