A hybrid material including tin oxides on the top of a Ge 0.3 Si 0.7-y Sn y /Si multiple quantum well structure has been first obtained. Tin oxides such as SnO and SnO 2 were formed as a result of phase transitions during the oxidation of polycrystalline tin films (β-Sn). The photoluminescence was demonstrated with a maximum intensity at about 2.34 eV, which corresponds to the band gap of SnO. The glow at the photogeneration point is seen in green. The photoluminescence from SnO is observed after the annealing in the temperature range of 300-400 °C. An increase in the annealing temperature leads to a sharp quenching of the photoluminescence. It is associated with the phase transition from SnO to SnO 2 . The growth of Ge 0.3 Si 0.7-y Sn y /Si multilayer structures is studied at the Sn content from 0 to 18%. It was found that GeSiSn compounds are thermally stable in the annealing temperature range of 300-550°C. In addition to the photoluminescence signal in the visible range from tin oxides, the photoluminescence signal in the infrared range of about 3 μm appears. It is formed from the GeSiSn/Si structure.
Quasi-two-dimensional GaTe layers were grown by molecular beam epitaxy on GaAs (001) substrates at Ts
= 450–520°C. The effect of the growth temperature on the GaTe surface morphology has been studied by scanning electron microscopy. It is shown that GaTe layer grown at high Ts
= 520°C exhibits pronounced surface relief anisotropy. This sample demonstrates also near band-edge photoluminescence (PL) at T = 11K with the peak energy of ∼1.72 eV, which can be associated with the emission of excitons bound at the acceptor. The nature of 1.45 eV and 1.57 eV peaks appearing in the PL spectra is also discussed in detail.
Fourier-transform infrared photoreflectance (PR) spectroscopy was used to study the energy spectrum of InSb/InAs/In(Ga,Al)As/GaAs metamorphic heterostructures with a superlattice waveguide at room temperature (RT). Theoretical calculations in the framework of the eight-band Kane model were performed to obtain a reliable knowledge of the actual energies of the most probable optical transitions. The experimental results were analyzed to determine the influence of the design features and stress balance on the energy spectra of the structures. Photoluminescence studies performed at 11 K and RT, as well as the determination of the internal quantum efficiency of luminescence, enabled us to characterize the emission characteristics of the structures, regardless of their waveguide efficiency. The structure with a 5-nm-thick GaAs insertion within the metamorphic buffer layer exhibited the highest probability of the main optical transition observed in the PR spectra as well as the highest luminescence intensity and quantum efficiency.
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