Manifestation of the upper hubbard band in the electrical conductivity of two-dimensional p-GaAs-AlGaAs structures

The Hall effect and electrical conductivity were studied in the temperature range of 1.7-300 K in Be-doped p-GaAs/AlGaAs multilayer structures with 15 -nm-wide quantum wells. Doping of the well itself and the adjacent barrier layer was used to create a situation when the upper Hubbard band (the A(+) centers) was occupied with holes and electrical conduction proceeded over t he states in this band. It is shown experimentally that the binding energy of A(+) centers increases significantly in the 15-nm-wide wells compared to this energy in the bulk, which is explained by the fact that the well size and the hole radius at the A(+) center are almost identical. The above rad ius was independently estimated from an analysis of the temperature depende nce of the hopping conductivity. (C) 2001 MAIK "Nauka/ Interperiodica".