The realization of efficient UV-C (200-280 nm) ligth emitting diodes (LEDs) is a current challenge to meet the requirements of numerous applications ranging from water, air and surface disinfection to short distance encrypted communication. However the efficiency of conventional UV-C LEDs is still low due to poor p-type doping and limited light extraction. In this context, the CEA/CNRS consortium involved in the realization of such emitters is developing a new strategy by using AlN nanowires (NWs). However, efficiency improvement now requires optimization of p-type doping, which will be the core of the present project, i.e. the growth, structural, optical and electrical characterization of p-type AlN nanowires. The growth of the structures will be performed by plasma-assisted molecular beam epitaxy in CEA-Grenoble IRIG/PHELIQS-NPSC. Electrical characterization will be made in Institut Néel following NW processing in clean room environment. The optical characterization will be made in collaboration between CEA and Institut Néel.

The electrical properties of semiconducting materials can be engineered by adding dopant atoms to the lattice, that donate or accept an electron from conduction or band valence, respectively. In this way the density of mobile charges can be tuned over several orders of magnitude. It is very well known that a transition from one type of dopant to the other kind will generate a so-called p-n junction, giving rise to rectifying current voltage characteristics and potentially light emission, for example in light emitting diodes. However, challenges remain to control and measure the electrically active doping levels in semiconducting materials with nm precision, especially in wide bandgap materials with high dopant activation energies. At nm scale the build in electric field at the pn junction gives rise to an electron beam induced current, allowing to study the junction properties.

Diamond is a semiconductor material with exceptional properties, like its high carrier mobility, excellent thermal conductivity and high breakdown voltage, which make it an ideal candidate for power electronic devices. Institut Neel is world leader in the fabrication of high-power diamond Schottky diodes and is continuously exploring ways for further improvements.

The aim of the internship is to manufacture gallium oxide capacitors and diodes. These devices will constitute the first technological building blocks which will then lead to the more accomplished realization of a transistor. To carry out this work, the trainee will have access to the NanoFab cleanroom tools (chemistry bench, lithography, etching, deposition) and morphological, electrical and optical characterization resources of the Néel Institute. The devices will be fabricated from gallium oxide substrates and thin films supplied by the ALOFET project partners (LMGP and PHELIQS). Experimental results obtained on thin films will be compared with structural studies carried out in parallel by other partners (LMGP, MEM).

L’objectif du stage est de fabriquer des condensateurs et des diodes en oxyde de gallium. Ces composants constitueront les premières briques technologiques qui conduiront ensuite à la réalisation plus aboutie d’un transistor. Pour effectuer ce travail, la ou le stagiaire aura à sa disposition les outils de la salle blanche NanoFab (banc de chimie, lithographie, gravure, dépôt) et les moyens de caractérisation morphologique, électrique et optique de l’Institut Néel. Les composants seront fabriqués à partir de substrats d’oxyde de gallium et de couches minces fournies par les partenaires du projet ALOFET (LMGP et PHELIQS). Les résultats expérimentaux obtenus sur les couches minces seront confrontés aux études structurales menées en parallèle par les autres partenaires (LMGP, MEM).