52 InAs/GaAs Quantum Dots Covered by Graded GaAsSb Strain Reducing Layer

摘要

Two systems of QDs are mainly used to extend operating wavelength of the GaAs based optoelectronic devices towards telecommunication wavelengths 1.3 μm or 1.55 μm, In(Ga)As/GaAs and GaSb/GaAs QDs (Cui et al, Physica E 45:173- 176, 2012). The most successful QD struc-tures combine In As QDs with InGaAs or GaAsSb strain reducing layer (SRL) to red shift the QD emission wavelength(Zhang et al, Sci Rep 2:477, 2012; Liu et al, Appl Phys Lett 86(14):143108,2005; Hospodková, Capping of InAs/GaAs quantum dots for gaas based lasers. In: Al- Ahmadi A (ed) Quantum dots: a variety of new applications. InTech, pp 27-46, 2012; Hospodková et al, J Crys Growth 370:303-306,2013). The tasks of the SRL are to re-duce the strain in QDs, to conserve their height and shape and to prevent their dis-solution. SRL also changes the hole localization: depending on the amount of Sb in GaAsSb, the hole may be localized in the QD (type-I heterostructure, less than about 14 % of Sb) or outside the QD in the SRL (type-II, more than 14 % of Sb); electrons are in both cases inside the QD. In this work, the decrease of the ground state emission energy was studied while keeping type-I band alignment between InAs QDs and GaAsSb SRL. The InAs/GaAs QD structures were prepared by low- pressure Metalorganic Vapour Phase Epitaxy (LP MOVPE) in Stranski-Krastanow growth mode. All samples were covered by the GaAsSb SRL with different Sb content and gradation and were studied by photoluminescence (PL). The theoretical simulations of the QD structures were done and compared with the PL results.