We compare properties of InAs/GaAs quantum dots (QDs) covered by InGaAs or GaAsSb strain reducing layers (SRLs) prepared by metal organic vapor phase epitaxy. Stronger red shift of QD emission was achieved with InGaAs SRL as compared to GaAsSb one with similar strain in the structure. This can be caused by the increase of QD size during InGaAs SRL growth. The heterojunction between InAs QDs and GaAsSb SRL changes from type I to type II between 13% and 15% of Sb in the SRL. Important advantage of GaAsSb SRL can be the possibility to change the overlap of electron and hole wave functions and QD dipole moment orientation by the composition of GaAsSb. We have achieved the highest PL intensity suggesting best wave function overlap near 13% of Sb in the SRL. Band alignment, transition probability and transition energy were calculated to help the interpretation of achieved results. (C) 2009 Elsevier B.V. All rights reserved.