D P as a function of electron concentration: (1) Sauer–Freise method calculation; (2) coordinate dependent diffusion method ((I) 0 < x <25 nm; (II) 25 < x <33 nm; (III) 33 < x <60 nm; (IV) 60 < x < 100 nm; (V) x >100 nm); (3—5) calculation according to Ref. [8], [9] and [6], respectively.