Photoluminescence investigation of Si as p-type dopant in AlGaAs grown by molecular beam epitaxy on high-index planes

Abstract

A systematic study of AlGaAs doped with Si in a wide doping range and grown on (N11)A GaAs surfaces by molecular beam epitaxy is reported. The growth conditions have been kept the same for all the surface orientations. Both electrical and photoluminescence measurements have been carried out to investigate the Si incorporation. All the samples display a p-type conductivity indicating that Si 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 observed that the (111)A planes have a lower optical and morphological quality. 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 samples grown on the (211)A planes both crystalline defects and shallow impurities are found. The results are explained in terms of the substrate orientation dependence of the ratio of single to double dangling bonds.