Degradation of GaN-based laser diodes after some time of operation appears usually as raised threshold current, lower slope efficiency, or increased voltage. We investigate stressed and non-stressed laser diodes using micro-electroluminescence (μEL) and micro-photoluminescence (μPL). In μEL, the stressed device exhibits darker regions, which are correlated with a red-shifted emission. Both observations indicate a lower carrier density in these darker areas. Our μPL measurements do not suggest a corresponding increased defect density in these regions. This study shows inhomogeneous pumping of the active region that can be explained by current path formation from non-uniform hydrogen distribution. Additionally a background of increased nonradiative recombination is found in the stressed device, which is unrelated to the conductivity degradation.
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