Red-emitting quantum well (QW) 630 nm laser diodes have many potential applications in industry and medicine. However, manufacture of such short wavelength lasers is impeded by severe electron leakage from the active region, which is predominantly attributed to loss of thermally activated electrons, via the inherently low conduction band offsets and possible inter-valley transfer to the lower energy X-band minima. To combat the high leakage current in such devices, we have implemented a multiquantum barrier (MQB) into the p-type cladding region of the device, and theoretically optimised the structure to reduce X-band transfer and predict effective enhancement to the intrinsic barrier height. (C) 2004 Elsevier B.V. All rights reserved.