Diamond is a promising material for high-power, high-frequency and high- temperature electronics applications, where its outstanding physical properties can be fully exploited. It exhibits an extremely high bandgap, very high carrier mobilities, high breakdown field strength, and the highest thermal conductivity of any wide bandgap material. It is therefore an outstanding candidate for the fastest switching, the highest power density, and the most efficient electronic devices obtainable, with applications in the RF power, automotive and aerospace industries. Lightweight diamond devices, capable of high temperature operation in harsh environments, could also be used in radiation detectors and particle physics applications where no other semiconductor devices would survive. The high defect and impurity concentration in natural diamond or high-pressure-high-temperature (HPHT) diamond substrates has made it difficult to obtain reliable results when studying the electronic properties of diamond. However, progress in the growth of high purity Single Crystal Chemical Vapor Deposited (SC-CVD) diamond has opened the perspective of applications under such extreme conditions based on this type of synthetic diamond. Despite the improvements, there are still many open questions. This work will focus on the electrical characterization of SC-CVD diamond by different measurement techniques such as internal photo-emission, I-V, C-V, Hall measurements and in particular, Time-of-Flight (ToF) carrier drift velocity measurements. With these mentioned techniques, some important properties of diamond such as drift mobilities, lateral carrier transit velocities, compensation ratio and Schottky barrier heights have been investigated. Low compensation ratios (ND/NA) < 10-4 have been achieved in boron-doped diamond and a drift mobility of about 860 cm2/Vs for the hole transit near the surface in a lateral ToF configuration could be measured. The carrier drift velocity was studied for electrons and holes at the temperature interval of 80-460 K. The study is performed in the low-injection regime and includes low-field drift mobilities. The hole mobility was further investigated at low temperatures (10-80 K) and as expected a very high mobility was observed. In the case of electrons, a negative differential mobility was seen in the temperature interval of 100-150K. An explanation for this phenomenon is given by the intervally scattering and the relation between hot and cold conduction band valleys. This was observed in direct bandgap semiconductors with non-equivalent valleys such as GaAs but has not been seen in diamond before. Furthermore, first steps have been taken to utilize diamond for infrared (IR) radiation detection. To understand the fundamentals of the thermal response of diamond, Temperature Coefficient of Resistance (TCR) measurements were performed on diamond Schottky diodes which are a candidate for high temperature sensors. As a result, very high TCR values in combination with a low noise constant (K1/f) was observed.

L’objectif de cette thèse porte sur la synthèse du diamant monocristallin dopé au bore par dépôt chimique en phase vapeur assisté par plasma micro-onde (MPCVD). Ces couches épitaxiées jouent le rôle de couches actives dans des composants pour l’électronique de puissance. Ces travaux s’inscrivent dans le cadre du projet Européen H2020 Greendiamond. Durant cette thèse, un traitement de gravure des défauts surfaciques des substrats de diamant HPHT par plasma Ar/O₂ a été mis au point. L’efficacité de ce traitement a été validée par diffraction des rayons X à haute résolution, spectroscopie Raman et cathodoluminescence. Cette étape s’est révélée essentielle pour l’amélioration des propriétés de transport de couches de diamant dopées au bore pour les applications en électronique.L’optimisation des conditions de croissance de couches de diamant faiblement dopées au bore (<10¹⁶ at.cm⁻¹) a permis la synthèse de films homoépitaxiés allant jusqu’à 5 µm d’épaisseur présentant une haute qualité cristalline. Les propriétés structurales et de transport de ces couches ont été corrélés en combinant différentes méthodes comme la spectroscopie Raman, la cathodoluminescence, la topographie X, l’imagerie MEB des défauts, les mesures par temps de vol et des mesures de Hall.Ces films de diamant dopés au bore ont été intégrés avec succès dans des composants électroniques comme des MESFET ou des diodes Schottky. / This PhD aims to synthetize boron doped single-crystal diamond epilayers by Micro-Wave Plasma Chemical Vapor Deposition (MPCVD) as active layers for power electronic devices. This work was performed in relation with the European H2020 Greendiamond project. A powerful Ar/O₂ plasma etching was optimized which allows the efficient elimination of defects in the subsurface of HPHT diamond substrates as confirmed by High Resolution X-ray Diffraction, Raman spectroscopy and Cathodoluminescence. This step proved to be crucial for the improvement of low boron doped-diamond layers carrier properties for electronic purposes.The optimization of growth conditions performed on low boron-doped diamond layers (<10¹⁶ at.cm⁻³) enabled the synthesis of high quality doped layers, 5 µm thick. The structural and transport properties of these layers were correlated by different techniques: Raman spectroscopy, Cathodoluminescence, X-Ray Topography, SEM imaging of defects, Transient Current Technique, Hall measurements.Finally, low boron doped epilayers were integrated with success in electronic devices such as MESFET or Schottky diodes.