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HL: Fachverband Halbleiterphysik
HL 46: Focus Session: AlGaN Materials for UV Emitters
HL 46.5: Topical Talk
Wednesday, March 28, 2012, 11:45–12:15, ER 164
Studies about defect reduction in AlGaN hetero structures — •Ferdinand Scholz1, Kamran Forghani1, Haoyuan Qi1, Mohammadreza Gharavipour1, Martin Klein1, Oliver Klein2, Ute Kaiser2, Benjamin Neuschl3, Klaus Thonke3, Richard Gutt4, and Thorsten Passow4 — 1Institut für Optoelektronik, Universität Ulm, 89081 Ulm — 2Zentrale Einrichtung Elektronenmikroskopie, Universität Ulm, 89081 Ulm — 3Institut für Quantenmaterie, Universität Ulm, 89081 Ulm — 4Fraunhofer-Institut für Angewandte Festkörperphysik, 79108 Freiburg
Owing to its large and tunable band gap, AlxGa1−xN is the key semiconductor for the development of UV light emitting devices. Currently, many groups study the realization of such LEDs emitting at wavelengths below 350nm. Obviously, the radiative efficiency decreases with decreasing wave length, which is most probably caused by the increasing defect density in such materials with increasing Al content x. We have investigated how the defect density in AlGaN structures with x 20 - 50% can be reduced by optimizing the respective MOVPE process. One possibility is the integration of in-situ deposited SiN interlayers which should act as dislocation blocking layers. This concept works excellently in GaN, but with only limited success in AlGaN. By transmission electron microscopy studies, we analyzed the functionality of SiN in AlGaN in more detail. UV LEDs grown on optimized AlGaN layers showed very high light output powers proving the success of our defect density reducing methods.