| dc.description.abstract | Silicon Carbide (SiC) radiation detectors are increasingly gaining recognition for their enhanced performance in diverse applications including nuclear radiation detection, functioning under high-temperature environments, x-ray detection, neutron detection and dosimetry. SiC comes out on top with its ability to operate efficiently in challenging environments. Compared to its primary competitor silicon (Si), 4H-SiC polytype has higher thermal conductivity, superior temperature stability, and a wider bandgap. In this thesis a scalable fabrication technique for n-type 4H-SiC Schottky diodes is proposed, serving as a stepping stone for the future fabrication of 4H-SiC-based detectors. The work encompasses the development and fine-tuning of photolithography processes, fabrication of 4H-SiC Schottky diodes, and their characterization. The photolithography process is based on the lift-off method. It involves two layers: (i) positive resist and (ii) a so-called lift-off layer to provide an undercut for easier removal of the resist. Such parameters as the exposure and development times were optimized. Optical microscopy and cross-sectional scanning electron microscopy were employed for optimizing the lithography process. Nickel, deposited by e-beam evaporation, was used for formation of Schottky diodes. Current-Voltage (IV) measurements show that the reverse-bias leakage current for most of the diodes is below the detection limit of the instruments used. The reverse saturation currents and the ideality factors are deduced from the fitting of the diode equation to the measurements for the forward bias. The lowest ideality factor and saturation current are 1.14 and 3.24∗10−21𝐴, respectively. The highest breakdown voltage obtained is 350 V. Capacitance-Voltage (CV) measurements have revealed the doping concentration in the epi-layer to be 1.2−1.3∗1016 𝑐𝑚−3. The depletion width at 100 V is deduced to be around 3 μm. The highest built-in voltage is found to be 1.6 V for 200 μm diodes, which is comparable with a theoretic value of 1.7 V. It is observed that smaller diodes (200 μm) demonstrate better characteristics, such as ideality factor, breakdown voltage and build-in voltage, compared to larger ones (2000 μm). We hypothesise that this is due to surface imperfections in the SiC epi-layer or dust particles from poor sample handling: As the diode size increases, there is a higher probability of a surface imperfection or a dust particle to occur between SiC and the metal, which will be detrimental for the Schottky diode. CV characterization of metal-oxide-semiconductor (MOS) structures is used to examine thermally grown silicon oxide (𝑆𝑖𝑂2) and aluminium oxide (𝐴𝑙2𝑂3), deposited by atomic layer deposition (ALD). MOS with thermally grown 𝑆𝑖𝑂2 reveal CV curves typical for a high-quality MOS structure, validating the insulating and passivating properties of the oxide. In comparison, ALD-grown 𝐴𝑙2 𝑂3 did not manifest reproducible and consistent CV characteristics. | eng |