Origin of defect luminescence in ultraviolet emitting AlGaN diode structures.

Light emitting diode structures emitting in the ultraviolet spectral range are investigated. The samples exhibit defect luminescence bands. Synchrotron-based photoluminescence excitation spectroscopy of the complicated multi-layer stacks is employed to assign the origin of the observed defect luminescence to certain layers. In the case of quantum well structures emitting at 320 and 290 nm, the n-type contact AlGaN:Si layer is found to be the origin of defect luminescence bands between 2.65 and 2.8 eV. For 230 nm emitters without such n-type contact layer, the origin of a defect double structure at 2.8 and 3.6 eV can be assigned to the quantum wells. A part of this research was carried out at the light source DORIS III at DESY. DESY is a member of the Helmholtz Association (HGF). We would like to thank A. Kotlov for excellent assistance in using beamline I at DESY. This work was partially supported by the Federal Ministry of Education and Research (BMBF), under Contract No. 13N9933 and Berlin WideBase initiative under Contract No. 03WKBT01D and the German Research Council within the Collaborative Research Center 787.pre-print465 K