Epitaxial self-assembled quantum dots (SAQDs) semiconductor heterostructures are ones of the modern prospective objects for light-emitting devices application [1]. Three-dimensional exciton localization into SAQDs results in high efficiency of radiative recombination. Using wide-gap semiconductors as a matrix for SAQDs enables to fabricate devices emitting in the visible spectral range. The present report is devoted to investigation of GaSbP/GaP SAQDs heterostructures. Up to now, just fully relaxed surface nanoislands [2] and SAQDs [3] were investigated, because GaSb and GaP have huge lattice mismatch about 10.5% [4]. We report to the formation of pseudomorphic GaSbP/GaP heterostructures with SAQDs.

Series of the structures with SAQDs were grown on the semi-insulator GaP (100)-oriented substrates by molecular beam epitaxy. SAQDs was formed at T_S = 420⁰C and T_S = 470⁰C.  Deposition of 1 monolayer GaSb was performed in atomic layer epitaxy mode.

Fig. 1. TEM plan view and cross-section (inset) images of the GaSb/GaP heterostructure with SAQDs.

The TEM plan view and cross-section images of the GaSb/GaP structure with SAQDs are presented in fig. 1 (a). The SAQDs arrays in the all structures are characterized by low density ( < 10⁸ cm^-2) and the lateral diameter of 80÷120 nm. The height of SAQDs is about 10 nm. As it clear from TEM images, SAQDs are pseudomorphic strained. Taking into account the huge lattice mismatch of GaSb and GaP [4] and large SAQDs sizes, formation of dislocation-free pseudomorphic SAQDs allows us to conclude, that it consists of ternary alloy GaSb_1-xP_x.

Fig. 2. Normalized steady-state PL spectra of GaSbP/GaP heterostuctures with SAQDs, grown at 420°C and 470°C, measured at 77 K and excitation density of 30 W/cm². 

All investigated structures demonstrate high photoluminescence (PL) intensity at non-resonant excitation to the GaP matrix and temperature 77 K. Blue shift of steady-state PL spectra with increasing T_S from 420⁰C to 470⁰C (see fig. 2) evidences increasing of GaP fraction in GaSb_1-xP_x/GaP SAQDs. Average alloy composition x = 0.6 at T_S = 420⁰C and x = 0.75 at T_S = 470⁰C were estimated using comparison of PL data with SAQDs energy spectrum calculations.

This work was supported by the Russian Foundation for Basic Research (Projects No. 13-02-00073), the Dynasty Foundation, the Presidential Grants No. SP-985.2013.5 and the programs of the Ministry of Education and Science of Russian Federation (contract 16.552.11.7091).

Reference
1.    D. Bimberg, M. Grundmann, and N. Ledentsov, Quantum Dot Heterostructures (Wiley, New York, 1999).
2.    K. Posilovic, T. Kettler, V. A. Shchukin, N. N. Ledentsov, U. W. Pohl, D. Bimberg, J. Fricke, A. Ginolas, G. Erbert, G. Trankle, J. Jonsson, and M. Weyers, Appl. Phys. Lett. 93, 221102 (2008).
3.    F. Bosc, J. Sicart, and J. L. Robert, J. Appl. Phys. 85, 6520 (1999).
4.    Vurgaftman, J. R. Meyer, L. R. Ram-Mohan, J. Appl. Phys. 89, 5815 (2001).   

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