In this study. H+ ion implantation was used to form high resistive regions in an AlGaInP/GaInP multi-quantum well (MQW) gain guided laser diode. The electrical derivative was used to characterize the properties of the fabricated laser diodes. The equivalent circuits were proposed to model the diodes for various structures. It was found that diodes fabricated with H+ ion implantation, have lower threshold current density and better carrier confinement characteristics. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.