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Title: Dielectrics for narrow bandgap III-V devices
Author: Vavasour, Oliver
ISNI:       0000 0004 7972 4422
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2018
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Indium antimonide is a narrow bandgap semiconduct or material with properties that make it ideal for mid-infrared opto electronics, ultra-high speed electronics and emerging spin-based quantum technologies. A significant limitation to its practical application is the lack of a dielectric technology for surface passivation and gate control. Modelling and analysis techniques for MOS capacitors have been tailored to InSb and verified, including nonparabolic band structure models and oxide capacitance extraction methods. High-field effects, such as Zener tunnelling and impact ionisa-tion, have been modelled to identify limitations on material doping (< 1016 cm-3) and quantisation effects have been similarly modelled to verify their impact on characterisation and analysis. InSb/Al2O3 MOS capacitor test structures have been fabricated to investigate a series of dielectric deposition processes. Wet chemical treatments using HCl were found to produce an InCl3 surface layer, but only if diluted in and rinsed with isopropanol. This layer was associated with a flat band voltage shift of +0.79V.HCl treatment was found to reduce hysteresis voltage but not significantly affect other figures of merit. In-situ plasma pretreatments were found to cause deterioration in MOSCAP structures, in particular increased DC leakage current. Post-metallisation annealing was investigated and optimum treatments determined to be around 300°C, 1 hr. At 400°C or greater, MOSCAP behaviour broke down, showing increased frequency dispersion and potential shift top-type behaviour. Some AlInSb layers were grown but provided limited information on the effect of Al composition, with layers significantly affected by growth methods and material strain. Alternative dielectrics were also examined. AlN offered slightly improved hysteresis but slightly increased interface trap density, whereas HfO2 produced dete-rioration in all figures of merit, particularly hysteresis voltage. These results pro- vide a foundation for further process development and integration into improved FET/diode device structures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering