The influence of the strain on the material quality of highly strained InAsP/InGaP multi-quantum well (MQW) systems has been studied. The main purpose of our study was to investigate and optimise the epitaxial crystal quality of different QWs structures in order to obtain the best well-barrier system. The strain-compensation technique enabled us to grow InAsP/InGaP-MQWs with strain exceeding +/-1% and as many as 20 wells without any material deterioration. The strain-compensated Structures have been grown by metalorganic vapor phase epitaxy (MOVPE) using TertiaryButylArsine (TBAs) and TertiaryButylPhosphine (TBP) as group V precursors. Photoluminescence (PL), High-Resolution X-ray Diffraction (HR-XRD), Transmission Electron Microscopy (TEM) have been used to study the MQW Structures. Net strain, shear strain and residual strain have been Used to evaluate the strain effects oil the material quality: strain compensation and abruptness of MQW interfaces Lire needed in order to obtain high performance material. In addition, in this system, the experimental data suggest that the influence of the strain compensation at the interface between well and barrier, which we define as 'symmetrical' strain, seems to be important in determining the quality of the MQW stacks. (C) 2004 Elsevier B.V. All rights reserved.