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The defence will be in English.
The recent SARS-COV2 pandemic has highlighted one of the many applications of UV radiation: sterilization. Aiming at replacing bulky and environmentally hazardous mercury lamps emitting at 255 nm, research is directed towards the development of solid-state solutions based on semiconductors. Aluminium gallium nitride (AlGaN) light-emitting diodes (LEDs) meet the requirements. In practice, the realization of such devices in planar geometry is limited by low electrical conductivity due to deep dopants and by difficult light extraction. In response, a promising alternative is being explored in my thesis: the nanowire (NW) geometry.
The first part of my defense will focus on the realisation of active areas emitting in the deep UV. AlN nanowires containing ultra-thin GaN quantum wells were successfully grown. After transmission electron microscopy (TEM) observations and cathodoluminescence (CL) measurements, quantum wells with thicknesses between 1 and 4 monolayers are found to emit between 239 and 304 nm.
The second part will be devoted to n-type doping of AlN nanowires with silicon. Based on current-voltage characteristics (I-V), I established that part of the dopants remained in a shallow state in addition to two deeper Si states. It is a first demonstration of the coexistence of these three states in the same set of samples.
Characterization of the entire LED structure is discussed in a last part. Devices showed typical rectifying behaviour and electroluminescence at 285 nm. I then identified the main transport mechanisms and limitation, this later being a difficult hole injection at the p-AlN / p-GaN interface.
