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Lise Lahourcade

Plasma-assisted molecular beam epitaxy of ( 11 2 ¯ 2 ) -oriented III-nitrides

Published on 6 October 2009

Thesis presented October 06, 2009

This work reports on the molecular-beam epitaxial growth of ( 11 2 ¯ 2 ) -oriented semipolar nitride semiconductors using m-sapphire substrates. The ( 11 2 ¯ 2 ) crystallographic orientation is predefined by AlN deposition on m-sapphire under N excess. On top of this AlN buffer layer, undoped or Si-doped two-dimensional GaN ( 11 2 ¯ 2 ) films are formed under Ga-rich conditions, with a stabilized Ga-excess adlayer of about 1.05±0.10 ML. In contrast, Mg tends to segregate on the GaN surface, inhibiting the self-regulated Ga excess film. Nevertheless, uniform Mg incorporation can be obtained, and p-type conductivity was achieved. GaN/AlN quantum wells are synthesized by deposition of the binary compounds under the above-described conditions. In the case of GaN/AlN quantum dots, the three-dimensional transition is induced by a growth interruption under vacuum. The reduction of the internal electric field in GaN/AlN nanostructures is confirmed by the blue shift of the photoluminescence spectrum and by the short photoluminescence decay times measured at low temperature. These results are consistent with theoretical calculations of the electronic structure.

MBE, nitrides, semipolar, LED, semiconductors

On-line thesis.