β-Ga₂O₃ For Power Electronic Devices

This thesis explores the development of processes to realise β-Ga2O3-based devices, focusing on etching protocols, dielectric characterisation, and forming ohmic contacts.This work started with developing a photoresist process to enable trench etching for bulk (001) β-Ga2O3 using SiNx hard masks and dry etching. SiNx was used as the hard mask due to it’s selectivity to β-Ga2O3, and the ease of removal compared to metal masks such as Cr. A photoresist protocol for patterning was developed and tested on Si, α-Al2O3, and β-Ga2O3. These processes are critical for isolating regions in devices like FinFETs and J-FETs, with SiNx demonstrated to be an effective hard mask. The research continued with a study which characterises Al2O3 (ALD) and SiO2 (PECVD) dielectrics on bulk (001) β-Ga2O3 through MIS capacitor fabrication. The effects of prolonged post-metalisation annealing were investigated using CV measurements and the Terman method, this showed a reduction in the hysteresis and interface traps (Dit) after annealing at 200°C. ALD Al2O3 exhibited superior interface quality compared to PECVD SiO2. TEM-EDX analysis revealed potential diffusion at the metal-dielectric interface. There was also an apparent decrease in film thickness after annealing. The final experimental section examines ohmic contacts on β-Ga2O3 using Ti/Al, Ti/Au, Ti/Ag, and Ti/W metalisations. Ti/Au is the most common metal which is used as an ohmic contact, hence deemed to be the most reliable to use as the standard ohmic contact to β-Ga2O3. Ti/Ag had the lowest resistance, however, limited data to agree with this, and so need to be repeated with more reliable experiments. This work lays the foundation for further work to form β-Ga2O3 devices. By investigating processes like etching, dielectric integration, and ohmic contact formation. Finally future work is outlined in the final Chapter, includes optimising material interfaces and refining measurement techniques.