《Advances in AlGaN-based Deep UV LEDs 》.pdf

Mater. Res. Soc. Symp. Proc. Vol. 831 © 2005 Materials Research Society E10.1.1 Advances in AlGaN-based Deep UV LEDs 1 2 1 2 1 1 M. H. Crawford , A. A. Allerman , A. J. Fischer , K. H. A. Bogart , S. R. Lee , W. W. Chow , S. 1 1 1 Wieczorek , R. J. Kaplar and S. R. Kurtz 1 Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA 2 Advanced Material Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA ABSTRACT Materials studies of high Al-content ( 30%) AlGaN epilayers and the performance of AlGaN-based LEDs with emission wavelengths shorter than 300 nm are reported. N-type AlGaN films with Al compositions greater than 30% reveal a reduction in conductivity with increasing Al composition. The reduction of threading dislocation density from the 1-5 x1010 -2 9 -2 cm range to the 6-9 x 10 cm range results in an improvement of electrical conductivity and -3 2 Al0.90Ga0.10N films with n= 1.6e17 cm and µ=20 cm /Vs have been achieved. The design, fabrication and packaging of flip-chip bonded deep UV LEDs is described. Large area (1 mm x 1 mm) LED structures with interdigitated contacts demonstrate output powers of 2.25 mW at 297 nm and 1.3 mW at 276 nm when operated under DC current. 300 µm x 300 µm LEDs emitting at 295 nm and operated at 20 mA DC have demonstrated less than 50% drop in output power after more than 2400 hours of operation. Optimization of the electron block layer in 274 nm LED structures has enabled a significant reduction in deep level emission bands, and a peak quantum w