Fabrication of High Speed GaN-based Transistors and DC-to-DC Converters.

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Next generation 5G wireless communication systems will require dramatic changes in the radio-frequency power amplifiers (PA) to meet the very high transfer data rate requirements (>10x higher than 4G). In addition, the 5G systems demand low power consumption but the conventional PA with a fixed voltage supply have poor efficiency with increasing frequency. Voltage-variable PA with lower energy losses, on the other hands, have potential to meet the 5G demands. However, lack of high switching speed (>100MHz) variable-voltage supply for the PA presents a challenge for high frequency system design.This project aims to realise ultra-high switching speed (200MHz) and high efficiency (>80%) voltage supplies using electronic switching devices made from gallium nitride (GaN) semiconductor for the next generation PA. Novel GaN device architecture which utilises multiple-gate structures will be fabricated to reduce voltage switching times and losses for high speed operations. Simulations and characterisations will be performed to understand the device physics and switching behaviours. Novel electronic control circuits for the proposed GaN devices in the voltage supplies will be designed. Finally, integration of the control circuits with GaN devices in a single chip will be carried out to reduce the unwanted parasitic and to boost the voltage supplies' switching performance to meet the 5G system demands.