We investigated the temperature dependence (10–180 K) of the photoluminescence (PL) emission spectrum of self-organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: (i) quenching due to the escape of carriers from the quantum dots and (ii) carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20–30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands.

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A systematic study of AlGaAs doped with Si in a wide doping range and grown on (N 11)A GaAs surfaces (N ≤ 3) 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.

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 (N 11)B GaAs surfaces (N ≤ 3) 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.

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