Controlling point defect populations in AlGaN deep UV LEDs.

Point defects are known to degrade LED performance by lowering efficiencies, maximum output power and device lifetimes. Here we show that growth temperature is a key variable, affecting both point defect concentrations and distributions. Cathodoluminescence and electron beam induced current measurements elucidate the role these defects play in carrier recombination within the wells. Combining such measurements with atomic force microscopy allows us to identify the growth mechanisms at play and help explain the point defect distributions observed. We find that in all cases, the presence of threading dislocations with a screw component led to the formation of spiral hillocks. Desorption of gallium along ridges and wide atomic terraces lead to blue-shifted quantum well emission energies but also impacted point defect populations. As growth temperatures were increased, dislocation mediated gettering counteracts a rising population of point defects. This restricts their impact below 1060°C, above which, performance regresses and point defects dominate.