OPTICAL-TRANSITIONS COUPLED WITH THE 2-DIMENSIONAL SURFACE SUBBANDS

The optical transitions taking place between two-dimensional surface s ubbands and bulk bands of semiconductors are investigated. It is shown that such transitions lead to a creation either of free carriers in b ulk bands and two-dimensional surface subbands, or of excitonic states coupled with two-dimensional subbands. The theoretical description of these processes is elaborated. The low-temperature photoluminescence spectra of the GaSe crystals are investigated and it is shown that a v ariation of the surface potential leads to the dissociation of exciton s coupled with two-dimensional surface subbands. The probability of su ch dissociations is evaluated. It is shown that these dissociations ca n lead, in particular, to an increase in the efficiency of the solar e nergy conversion in hydrogen energy. (C) 1998 Elsevier Science B.V. Al l rights reserved.