Spatially resolved electroluminescence of InGaN-MQW-LEDs

Electroluminescence (EL) is the most significant measure for light-emitting diodes since it probes the most relevant properties of the fully processed device during operation. In addition to the information gained by conventi onal spectrally resolved EL, scanning micro-EL provides spatially resolved information. The devices under investigation are InGaN/GaN-LEDs with single peak band-band emission at about 400 nm grown by MOVPE on sapphire substra tes The mu -EL-characterization is performed as a function of injection current densities and the emission is investigated from the epitaxial layer as wel l as from substrate side. Spatially resolved wavelength images reveal emiss ion peaks between 406 nm and 417 nm corresponding either to In fluctuations of 1 %-1.5 % or local fluctuations of piezo electric fields. Beside the in formation on the emission wavelength fluctuations mu -EL is used to determi ne the temperature distribution in the LEDs and to investigate transparent contacts.