INTRA-LAYER AND INTER-LAYER HOPPING TRANSPORT AND THE METAL-NON-METALTRANSITION IN THE 2-DIMENSIONAL AND 3-DIMENSIONAL SYSTEMS OF DELTA-DOPED SEMICONDUCTORS

A percolation theory approach is taken to investigate electron hopping transport and the metal-non-metal transition in n-type delta-doped se miconductor systems. The activation energy is calculated for infer-lay er hopping events in multiple-delta-layer systems. The corresponding c ritical sheet density for the metal-non-metal transition is calculated , and it is shown that this increases for increasing delta-layer separ ation. Consideration of a single delta-layer has allowed the determina tion of the activation energy as a function of the sheet density of do nors, for intra-layer hopping. The critical concentration sigma(c) of donors for the metal-non-metal transition in this truly two-dimensiona l system has been found to be similar to 3.4 x 10(10)cm(-2) in a GaAs host. Furthermore, by considering a range of host semiconductor crysta ls, the concentration induced metal-nonmetal transition in a two-dimen sional distribution of donors of Bohr radius lambda is shown to be giv en by root sigma(c) lambda approximate to 0.19. (C) 1997 Elsevier Scie nce Ltd.