Analysis of Current Transport Layer Localized Resistivity Increase After High Stress on InGaN LEDs

This work reports on the effects of high current stress on InGaN-based light-emitting diodes (LEDs.) The analyzed devices are high power blue LEDs with an emitting area of 1 mm2 subjected to a constant current stress at increasing current until the catastrophic device failure. By means of optical, electrical and photoluminescence analysis we hypothesize that the optical power decrease is related to a degradation in the current transport layers of the devices. The effect has been modelized as a gradual and localized increase in the current transport layer resistance; the model has been validated by means of SPICE electrical simulations. The results clearly indicate that, to extend the operating range of high-power devices, it is crucial to control the current crowding effect, which is here considered to play a significant role in the degradation in the current transport layer.