Effect of AlGaN/GaN strained layer superlattice period on InGaN MQW laser diodes

AlGaN/GaN strained layer superlattices have been employed in the cladding l ayers of InGaN multi-quantum well laser diodes grown by metalorganic chemic al vapor deposition (MOCVD). Superlattices have been investigated for strai n relief of the cladding layer, as well as an enhanced hole concentration, which is more than ten times the value obtained for bulk AlGaN films. Laser diodes with strained layer superlattices as cladding layers were shown to have superior structural and electrical properties compared to laser diodes with bulk AlGaN cladding layers. As the period of the strained layer super lattices is decreased, the threshold voltage, as well as the threshold curr ent density, is decreased. The resistance to vertical conduction through p- type superlattices with increasing superlattice period is not offset by the increase in hole concentration for increasing superlattice spacing, result ing in higher voltages.