The low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE) of tensile AlGaInAs multi-quantum wells (MQWs) for transverse magnetic (TM) 1.3 mum emitting lasers is presented. Al-containing wells have been mostly studied with compressive strain for transverse electric (TE) lasers. In this study, we report on highly tensile-strained AlGaInAs well layers (-0.72 to - 1.65%) grown with compressive-strained AlGaInAs barrier layers (0.64%). The good agreement of high-resolution X-ray curves and simulated curves indicates that good crystalline quality and abrupt heterointerfaces are obtained. An enhanced separation between light hole and heavy hole transitions is clearly observed by room-temperature photoluminescence as the strain increases. From broad-area laser results, it was observed that the strain had a low impact on the laser internal loss, the quantum efficiency and the transparency current density, which was as low as 0.32 A/cm(2) for a 6 QW structure. On the opposite, a doubling of the gain parameter go when the strain increases from -0.72 to - 1.65% was clearly observed. This result is associated with a 40% threshold density reduction on 300 pm long lasers. These investigations show that highly tensile-strained layers are very promising for the realisation of high-speed lasers. (C) 2004 Elsevier B.V. All rights reserved.