3 and

1.55 μm. A recent promising approach is to extend the emission wavelength of self-assembled InAs/GaAs to these two regions by using a GaAs capping layer by Sb incorporation [13–16], and even a longer wavelength has already been obtained click here [15, 16]. The strong redshift has been attributed to a type II band alignment for high Sb contents [17]. A few studies aiming to analyze the emission evolution with the amount of Sb [18, 19], as well as the microstructures of these QDs, have been carried out recently by means of scanning transmission electron microscopy (STEM), atomic force microscopy (AFM), and conventional transmission electron microscopy (CTEM). The results demonstrate that they have the significant find more difference from

those of GaAs-capped QDs [17, 19–21]. However, there is almost no report about the effect of Sb sprayed on the surface of InAs immediately prior to depositing the GaAs capping layer, from the perspective of crystal structure. Since Sb incorporation will result in the formation of GaSb with a larger lattice constant, this should help provide a strain relief layer effectively bridging the lattice mismatch between InAs QDs and GaAs matrix. Then, the strain induced in the QDs during capping should be reduced, which will influence the QD size, shape, composition, defect, and dislocations. It is known that the properties of promising devices relying on quantum dot properties are compromised due to the presence of defects generated when the quantum dots are capped [22–25]. Therefore, a fundamental understanding about the defects of the QDs with and without

Sb incorporation before GaAs capping is very important for device applications and will lead to better methods for minimizing the impact of these defects and dislocations. High-resolution transmission electronic microscope (HRTEM) structural imaging enables us to see atoms at their real VS-4718 chemical structure locations and thus gives us detailed information about lattice misfit, defects, and dislocations. In this work, we used cross-sectional HRTEM to see how defects and dislocations are generated during the growth of InAs/GaAs QDs and the impact of the addition of Sb atoms. Methods The two samples studied ID-8 were grown by molecular beam epitaxy in an AppliedEpi GenIII system (Veeco, Plainview, NY, USA) on (100) GaAs substrates with a 200-nm-thick GaAs buffer layer. One sample with InAs/GaAs QDs capped by GaAs was named sample 1, and the other sample with InAs/GaAs QDs spayed by Sb flux for 30 s before the GaAs capping layer was named sample 2. Gallium and indium fluxes were supplied by conventional thermal sources, while As and Sb fluxes were provided by valved cracker sources. The growth rates determined by monitoring the RHEED oscillations were 0.4 and 0.035 monolayers/s for GaAs and InAs, respectively, and the measured beam equivalent pressure for Sb was 9.7 × 10-8 Torr. The As overpressure for all the GaAs and InAs growth steps was 2 × 10-6 Torr.