Investigation of Si as an n-type dopant in AlGaAs grown by molecular beam epitaxy on high index planes

Abstract

We present a detailed study of n-type silicon doped AlGaAs in a wide range of silicon concentrations. The samples have been grown on (100) and (N11)B GaAs surfaces by molecular beam epitaxy using the same growth conditions for all the surface orientations. Electrical, photoluminescence and secondary ion mass spectrometry measurements have been carried out to investigate the Si incorporation. The total amount of Si incorporated is independent of the growth plane. All the samples display an n-type conductivity, indicating that Si incorporates predominantly on the Al/Ga sites. In general, the samples grown on substrates which present steps in their surface structure [(211)B and (311)B], have a better quality than those grown on flat surfaces [(111)B and (100)]; in particular the best quality is obtained for the samples grown on (311)B plane which display photoluminescence spectra with narrow excitonic structures and high values of Hall mobility and free carrier concentration. On the contrary, the worst results are found for the samples grown on the (111)B surface which are characterized by low mobility values and broad photoluminescence spectra with important defect emissions.