Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 27: GaN: preparation and characterization I
HL 27.5: Talk
Wednesday, March 25, 2009, 10:45–11:00, BEY 81
Structure and electronic properties of dislocations in GaN — •Philipp Ebert1, Lena Ivanova2, Svetlana Borisova1, Holger Eisele2, Ansger Laubsch3, and Mario Dähne2 — 1Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany — 2Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany — 3OSRAM Opto-Semiconductors GmbH, 93055 Regensburg, Germany
Group-III nitrides developed rapidly toward the materials of choice for green to ultraviolet optoelectronics. Unfortunately, GaN substrates are still suffering from high dislocation densities, far above that of zincblende type III-V semiconductor substrates. This presence of high dislocation densities is detrimental for optoelectronics, because dislocations can act as recombination centers. Therefore, we investigated the type, spatial distribution, the projected line direction, and electronic properties of dislocations in n-type GaN by scanning tunneling microscopy. The dislocations were found to form localized bunches of entangled non-parallel dislocation lines. Within these bunches perfect dislocations with a/3{1120} Burgers vectors were uncharged, while Shockley partials with a/3{1120} Burgers vector and the related intrinsic type-2 stacking fault were negatively charged. The charges are traced to different charge transfer levels associated to the particular core structure. The observations suggest that the dissociation of dislocations may be responsible for the insertion of detrimental gap states in n-type GaN.
This work is supported by the DFG through SFB 787 and Eb 197/3-1.