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An approach is presented for comprehensive and reliable analysis of the surface photovoltage (SPV) amplitude and phase spectral behaviour in various semiconductor materials and structures. In this approach the SPV signal is represented as a radial vector with magnitude equal to the SPV amplitude and angle with respect to the x-axis equal to the SPV phase. This model is especially helpful in complicated nanostructures, where more than one SPV formation processes arises during the spectrum run. The value of the proposed model has been demonstrated by the successful explanation of seemingly contradictory SPV amplitude and phase spectra of AlAs/GaAs superlattices with embedded GaAs quantum wells, grown on different GaAs substrates. This has provided useful information about the investigated nanostructures. The need for simultaneous examination of both SPV amplitude and SPV phase spectra in order to obtain a correct understanding of the experimental data is emphasized.

Rolled-up semiconductor tubes of various diameters made of alternating In0.215Ga0.785As/GaAs layers have been investigated by means of Raman scattering. The optical and acoustic phonon modes of individual tubes have been studied and compared with the characteristics of the surrounding material. After tube formation, the frequency of the phonon modes shifts with respect to the as-grown material and disorder activated modes are observed. The frequency shifts are related to the residual strain in the tubes through the deformation potential approximation. Good agreement with atomistic valence force field simulations and x-ray micro-diffraction measurements is found. By comparison with x-ray data, a Raman strain constant K = 0.65 is proposed for In0.215Ga0.785As. In the low frequency range, acoustic mode doublets are observed on the tubes that are absent in the surrounding material. They show clear evidence of the formation of periodic superlattices after the rolling-up process, and give insight into the quality of their interfaces.

We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.

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