Characterization and reliability of blue and white GaN-based LEDs submitted to current and thermal stress

The aim of this thesis work is to analyze reliability of blue and white GaN-based commercial LEDs. Reliability is indeed one of the key factors for devices success in the market of lighting solutions. Temperature and driving current are the main causes of degradation of LEDs. In order to understand the degradation mechanisms of these devices two types of stresses have been carried out, current and thermal stress and pure thermal stress, and electrical, optical and thermal measurements have been performed. The results obtained at the end of this work show several types of degradation mechanisms which influence LEDs both electrical and optical properties / Caratterizzazione e affidabilità di LED blu e bianchi basati su nitruro di gallio sottoposti a stress in corrente ed in temperatura