A study of the photovoltaic properties of the GaAs-based solar cells with InGaAs quantum wire had been conducted. The research included the investigation of the photovoltage rise and decay transients, spectral photovoltage dependences at different temperatures. The objects investigated were GaAs-based solar cells with InGaAs quantum wire (QWR) embedded into space-charge-region of p-i-n junction. Samples with different In content and size of InGaAs nanoobjects had been created using molecular beam epitaxy. Unlike the reference cell, the ones containing the InGaAs QWR had shown higher sensitivity in the energy range 1.2 - 1.38 eV. This is caused by the spatial separation of electron-hole (e-h) pairs excited in the QWR due to band-to-band transition. Under selective excitation of the e-h pairs only in the InGaAs quantum wire the photovoltage rise transient is slower compared to the e-h generation in GaAs. This effect is explained by charge carriers release from the InGaAs quantum well into delocalized states of the surrounding GaAs. It was determined that the InGaAs quantum wires increase the recombination rate of the non-equilibrium carriers in the temperature range 80 to 290 K, which means that the quantum wires are the additional recombination centers.
The luminescent properties of InGaAs/GaAs heterostructures with InGaAs nanoscale objects were investigated. Multilayer heterostructures were grown using molecular beam epitaxy technique. The shapes of the photoluminescence spectra were studied in the temperature range from 10 K to 290 K. The electronic spectrum of heterosystems as well as the energy of interband transitions for InGaAs nano-objects were calculated for different sizes and InGaAs component composition. It is shown that the shape of the photoluminescence spectra is determined by the Gaussian distribution of the energy of band-to-band optical transitions between the ground states of the conduction band and valence band of nanoscale objects. The physical reason for the observed energy dispertion is the variation of sizes, heterogeneity of component composition and strain relief in the ensemble of InGaAs nano-objects. Non-monotonous temperature dependence of the width of the photoluminescence spectra indicates the existence of temperature-dependent redistribution of photoexcited charge carriers between neighbouring nanoislands having different energy of the ground states.
Structures with one-dimensional quantum objects in intermediate band are promising for their application in solar cells and photodetectors. We present analysis of dark current-voltage characteristics, photo-voltage decay and photo-voltage spectra for this structures in comparison with reference GaAs based structures. It has been shown that InGaAs quantum wires make a significant influence on J-V dependences and photo-voltage spectra. InGaAs QWRS are additional recombination centers and transitions between them dominated over by Shockley-Read-Hall recombination at low bias. The InGaAs/GaAs sample shows a significantly higher photo-voltage in the spectral range of 1.25-1.37 eV, as compared to a reference GaAs p-n junction, due to intermediate band transitions in the quantum wires.