PHOTOLUMINESCENCE INVESTIGATION OF SI AS P-TYPE DOPANT IN ALGAAS GROWN BY MOLECULAR-BEAM EPITAXY ON HIGH-INDEX PLANES

A systematic study of AlGaAs doped with Si in a wide doping range and grown on (N11)A GaAs surfaces (N less than or equal to 3) by molecular beam epitaxy is reported, The growth conditions have been kept the sa me for all the surface orientations. Both electrical and photoluminesc ence measurements have been carried out to investigate the Si incorpor ation. Ail the samples display a p-type conductivity indicating that S i incorporates predominantly on the As sites. A lower C incorporation on the (111)A surfaces than on (211)A and (311)A has been found. We ob served that the (111)A planes have a lower optical and morphological q uality. However, the values of the Hall mobility, of the free carrier concentration and of the photoluminescence efficiency are not degraded . The samples grown on the (311)A planes show a higher optical quality with shallow-impurity-related optical transitions, while in the sampl es grown on the (211)A planes both crystalline defects and shallow imp urities are found. The results are explained in terms of the substrate orientation dependence of the ratio of single to double dangling bond s.