Thesis presented November 08, 2011

Abstract:
Quantum well ZnO nanowires and p-type doping by nitrogen ion implantation are studied to make ultraviolet light-emitting diodes. O-polar pyramids and Zn-polar nanowires on sapphire and ZnO substrates are grown. Organized growth of nanowires on a masked Zn-polar ZnO is demonstrated. Similarly, GaN pyramids and nanowires are grown on Ga and N-polar GaN respectively. On sapphire, the dislocation elimination in the underlying pyramids is analyzed. Nanowires with no structural defects allow the growth of ZnO/Zn_(1-x)Mg_xO core-shell quantum wells. Plastic relaxation is studied, and the Mg composition is optimized to avoid it and attain an internal quantum efficiency as high as 54%. Concerning ion implantation, the defects are identified before and after annealing. They disappear in the near-surface, which lead to an easier recovery of nanowires compared to bulk ZnO. However, a recovered material with activated acceptors is not obtained.

Keywords:
Quantum wells, Ion implantation, Nanowire, Transmission electron microscopy

On-line thesis.