Thesis presented November 15, 2013

Abstract:
This work reports on the realization by metal organic vapor phase epitaxy of visible light emitting diodes based on GaN wires grown on Si(111) with a focus on understanding the wires growth mechanisms and the properties of InGaN/GaN core/shell heterostructures grown around them. First we report the MOVPE growth of –c oriented GaN wires on sapphire. We demonstrate that the injection of silane during the growth induces the formation of a SiN_x passivation layer around the GaN wires, preventing the lateral expansion. The silane flow can be stopped after a certain time without modifying the wire geometry. This phenomenon is used to control the position of the InGaN/GaN multiple quantum well shells along the wires. The wire growth on sapphire has then been transferred to silicon substrate thanks to the deposition of a thin AlN buffer layer prior to the wire growth. The deposition of InGaN/GaN core/shell heterostructures on the non-polar m-plane side facets of the wires and the influence of different growth parameters on the light emission properties of the quantum wells are then studied. Several types of quantum wells grown on different facets of the wire surface are observed. These different families emit light at different wavelengths that have been indexed thanks to cathodoluminescence mapping. The indium concentration in the quantum wells deposited is estimated between 8 and 24 %, depending on the growth conditions. This estimation has been made by comparing the emission wavelength of the quantum well to the recombination energy of electrons and wells simulated using the 8x8 band k.p theory for electron and hole masses. Finally, complete LED structures have been deposited on GaN wires by MOVPE and blue electroluminescence at 450 nm has been measured on single wires and assemblies of wires on Si(111).

Keywords:
GaN, Nanowires, Heterostructures, Growth, Optics, Device