| 1. |
- Donchev, V., et al.
(author)
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Photoluminescence study of AlAs/GaAs superlattices containing enlarged wells
- 2000
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:1, s. 224-227
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Journal article (peer-reviewed)abstract
- Photoluminescence (PL) spectra of MBE grown short-period AlAs/GaAs superlattices with one or two enlarged wells (5 and 12 nm) have been measured at 2 K. Sharp PL peaks corresponding to excitonic transitions between the lowest electron and heavy-hole states in the enlarged wells are observed. The excitonic transition energies are calculated by means of an envelope function based model, taking into account the exciton binding energies. The model incorporates a smooth potential at the interfaces, which is represented by a diffusion potential, the diffusion length being a parameter. The calculated and experimentally observed excitonic transition energies agree well if diffusion lengths of 3.5 and 4.5 monolayers are considered in the samples with and without a buffer layer, respectively. These values are consistent with the complicated nature of the growth kinetics and mechanisms of quantum heterostructures. The PL spectra reveal also complicated structures connected with the superlattice. Their qualitative discussion confirms the smooth potential model. Thus, an attempt is made to extend the analysis of complicated AlAs/GaAs heterostructures towards real interfaces, which is essential for advanced device fabrication.
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| 2. |
- Shtinkov, N., et al.
(author)
-
Effect of non-abrupt interfaces in AlAs/GaAs superlattices with embedded GaAs quantum wells
- 2000
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In: Vacuum. - 0042-207X .- 1879-2715. ; 58:2, s. 561-567
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Journal article (peer-reviewed)abstract
- In the present paper, we investigate the effect of the non-abrupt interfaces on the electronic and optical properties of short-period AlAs/GaAs superlattices with embedded GaAs quantum wells. The lateral disorder and the component interdiffusion at the interfaces are averaged over the layer planes and are effectively represented by a diffusion concentration profile in the growth direction. The diffusion length LD is used as a parameter characterizing the degree of interface broadening. The electronic structure calculations are made using the sp3s* spin-dependent empirical tight-binding Hamiltonian, the virtual crystal approximation, and the surface Green function matching method. The dependencies of the lowest electron (E1), heavy hole (HH1), and light hole (LH1) bound states on the diffusion length are calculated for LD from 0 to 4 monolayers. It is found that the energies of the transitions (E1-HH1) and (E1-LH1) increase as LD increases. The results obtained are compared with photoluminescence data for MBE-grown samples. It is found that the degree of interface broadening depends on the growth temperature and on the sample geometry. The diffusion lengths calculated from the experimental data follow the expected trends, revealing a good qualitative agreement between theory and experiment.
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