Current dependence of electro-optical parameters in green and blue (AlIn)GaN laser diodes

Abstract
We present a detailed study of laser characteristics of blue and green R&D laser diodes grown on free standing GaN substrates with c-plane orientation under forward current condition. The slope efficiency of the blue emitting device exhibits a constant value over the entire operation range. In contrast to that, the green laser shows a decrease in slope efficiency with increasing current. A reduction of slope efficiency can be caused either by increasing internal losses or decreasing injection efficiency. A series of different mirror coatings is used to correlate the decreasing slope efficiency with a slight decrease of the injection efficiency as a function of current density. Furthermore, the reduction of the injection efficiency does not depend on the junction temperature. We could also verify that the internal losses are not temperature sensitive for blue and green laser diodes.