Evaluation of multiquantum barriers in bulk double heterostructure visible laser diodes

Three bulk (Al/sub x/Ga/sub 1-x/)/sub 0.5/In/sub 0.5/P double heterostructure (DH) lasers were designed and fabricated to examine the effect of incorporating multiquantum barrier (MQB) structures. The first laser, used as a reference, has a conventional structure, while the remaining lasers include MQB structures, one designed to achieve a virtual barrier of 75 meV, the other having a transmission window up to 100 meV above the bulk barrier height. Measurements show a reduction of up to 31% in the room temperature threshold current and an increase in characteristic temperature of 20 K by the inclusion of the optimized MQB structure in comparison with the reference laser. However, since the leaky MQB design also shows a significant room temperature improvement over the reference laser we suggest that the device improvements produced by the MQB structures are not solely due to the formation of a virtual barrier.