AlAsSb- and InGaAs(:Si)-layers have been grown by molecular beam epitaxy lattice matched to InP-substrates and characterized by X-ray diffraction, photoluminescence (PL) and capacitance-voltage profiling. Multi-quantum-well structures with 10 periods of 6 um InGaAs-wells and 15 nm of AlAsSb-barriers were investigated in terms of interface abruptness and Si-doping. The PL full-width at half-maximum (PL-FWHM) at room temperature of undoped structures was reduced from 137 to 84 nm due to growth interruptions at interfaces under As-flow and with In and Sb segregation compensation. The Si doping by co-deposition of the InGaAs wells was compared to δ-doping centered to the wells. Uniformly doped InGaAs-wells with a Si concentration of I x 10(19)atoms/cm(3) showed an increased PL-FWHM of 178 nm due to degradation of interfaces. By δ-doping with 0.05 monolayers of Si in the middle of the wells the PL-FWHM could be reduced to 122 nm and the intensity of the signal could be increased compared to the uniformly doped quantum wells. © 2005 Elsevier B.V. All rights reserved.