Investigation Of Optical Transitions Research Articles

Investigation of optical transitions and electrical properties in LaVO3/SrTiO3 heterostructure

Investigation of optical transitions and electrical properties in LaVO3/SrTiO3 heterostructure

Investigation of optical transitions in a SiGeSn/GeSn/SiGeSn single quantum well structure

A SiGeSn/GeSn/SiGeSn single quantum well structure featuring type-I band alignment was comprehensively characterized. Three pump lasers with different penetration depths and photon energies were used to pinpoint the optical transition characteristics of the sample. The carrier generation, redistribution, and recombination under each pumping condition were analyzed in detail. By comparing the temperature-dependent photoluminescence spectra of the GeSn quantum well with that of SiGeSn and GeSn thin film samples possessing similar Si and Sn compositions, the optical transition mechanism was clearly identified.

Photoreflectance spectroscopy of coupled InxGa1−xAs/GaAs quantum wells

The investigation of optical transitions in strained In0.045Ga0.955As/GaAs multiple quantum wells is presented. The structures were grown by molecular beam epitaxy for different GaAs barrier thickness (1, 3, 5 and 9 monolayers) and for different numbers of wells (3 and 4). The photoreflectance spectra of these samples have been measured at liquid nitrogen temperature. The origin of various spectral features have been assigned by using the results of the envelope function calculation and taking into account the effects of strain and exciton binding energy. The quantum wells are type I for the electron-heavy hole system and type II for the electron-light hole system, with the electrons and heavy holes confined in the InxGa1−xAs layers and the light holes in the GaAs barrier regions. The influence of changes of barrier thickness on the confined transitions including parity-forbidden and indirect in the real space light hole ones has been studied. The splitting of the fundamental heavy hole state has been derived.

Investigation of optical transitions in superlattices using photovoltage spectra

This paper presents the experimental set-up and the measurement procedures of the photovoltage technique and reports a photovoltage spectroscopy study of the subband structures and the optical transitions in AlAs/GaAs superlattices at different temperatures ranging from 18 to 300 K. Below 100 K, the photovoltage spectra reflect the step-like distribution of the two-dimensional state density, and a sequence of distinct exciton transition peaks have been observed. The peaks are identified according to the selection rule of optical transitions and the calculated results. The experiments show that the photovoltage changes considerably with temperature. The mechanisms for the photovoltaic effect of superlattice and quantum well structures are given and the changes in photovoltage with temperature are discussed.