Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: GaN: preparation and characterization

HL 51.3: Talk

Friday, March 30, 2007, 11:30–11:45, H13

Vertically increasing well thickness and In content in GaInN MQWs due to V-shaped pits — •Heiko Bremers, Lars Hoffmann, Daniel Fuhrmann, Holger Jönen, Uwe Rossow, and Andreas Hangleiter — TU Braunschweig, Institut für Angewandte Physik, Mendelssohnstr. 2, 38106 Braunschweig

So far the origin of the high efficiencies of light emission in the GaInN based quantum wells (QW’s) is still under debate. It is commonly believed that the suppression of non-radiative recombination processes is due to fluctuations of In concentration, which could lead to a localization of carriers. Recently another approach has been proposed which shows that V-shaped pits with reduced well thicknesses on the facets might be responsible for the suppression of non-radiative recombination. In this work we investigate the influence of V-shaped pits on the growth of GaInN-GaN MQW’s by TEM and x-ray diffraction measurements. We have grown different MQW’s by a low-pressure MOVPE and studied the influence of the number of QW’s as well as of the depth of V-shaped pits. During the growth of the samples a material transport takes place from the pits to the c-plane. We show that the thickness of the GaInN QW’s and of the GaN barriers is increased due to material transport. With increasing number of quantum wells the diameter of the pits increases, which leads to a superlinear increase of these thicknesses. We present a model which describes the change in thickness due to material transport. Additional photoluminescence measurements performed on our samples exhibit a redshift as well as a broadening with increasing number of quantum wells.