Limitierende Mechanismen für (Ga,Al,In)N-basierte LED-Strukturen im grünen und ultravioletten Spektralbereich (English shop)

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The group III-nitride compound semiconductors, i.e. the compounds of gallium, aluminium and indium with nitrogen, today form the basis for modern light emitters in the visible spectral range. Despite the high efficiencies achieved so far in the blue and violet spectral range, a strong drop in efficiency is observed for ultraviolet and green emitting LEDs based on this material class. The present work addresses the question of the causes of this pronounced decrease in efficiency and points out ways of optimisation towards higher efficiency.

After an introduction to the material class of the group III-nitrides, the fundamentals of the growth method used, metalorganic vapour phase epitaxy (MOVPE), as well as the fundamentals of the applied characterisation methods are presented. In the following chapters it is then shown that for nitride-based LEDs a high efficiency can only be achieved if the charge carriers can be screened from the numerous defects. The basis of this defect screening is the decoration of each individual defect with a V-pit. It is shown that this concept is universally applicable throughout the entire (In,Ga,Al)N system, irrespective of whether visible-emitting In-containing LEDs or UV-emitting In-free LEDs are considered. Starting from highly efficient blue LED structures with low In content, the growth of InGaN/GaN quantum wells with high In content is investigated on the one hand. On the other hand, the insights gained are also transferred to In-free LED structures with a view to optimising the efficiency.