Investigation of the time-dependent failure of InGaN-based LEDs submitted to reverse-bias stress

摘要

Within this paper, the role of high electric fields and deep depletion in the degradation of the gallium nitride material system is analyzed by means of reverse bias step-stress tests and constant voltage stress on LED chips. The degradation, monitored by means of electrical and optical techniques, consists in an increase of the leakage current flowing through localized spots, due to a higher density of defects caused by the high electric field. Eventually, the devices fail due to the very high local power dissipation, leading to the melting of the semiconductor and of the semitransparent contact layer.