Thermal degradation in InGaN quantum wells in violet and blue GaN-based laser diodes

The effects of thermal damage in AlInGaN-based light emitting devices, with In_xGa_1-xN single quantum well (QW) as an active layer, from violet to blue emissions are reported. The intensity of the electroluminescence (EL) of laser diodes (LDs) grown at high temperatures (>1000 °C) for p-type layers was drastically decreased above approximately 440 nm. The threshold current and slope efficiency of the LDs were significantly deteriorated with an increase in the lasing wavelength from 405 to 435 nm. From the TEM and AFM measurements, the surface degradation and In phase separation was observed in the blue InGaN QW structure due to the surface migration of adatoms and the spinodal decomposition during the high temperature ramp-up and long growth time for the p-type layers, respectively.