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Innovative Approaches for AlGaN/GaN-based Technology

Baltynov, Turar (2016) Innovative Approaches for AlGaN/GaN-based Technology. PhD thesis, University of Sheffield.

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Abstract

Gallium Nitride (GaN) has been proven to be a very suitable material for advanced power electronics on account of its outstanding material properties. Today, researchers are exploring GaN-based high electron mobility transistors (HEMTs) for conventional as well as high-end solutions in the range of 600 – 1200 V. However, thermal and power density limitations have impeded the achievement of the peak operational capability of AlGaN/GaN HEMTs. GaN-on-Diamond technology has proven to be a feasible solution to reduce thermal resistance and increase power density of AlGaN/GaN HEMTs for RF applications. The work presented in this thesis is focused on the realisation of high-voltage GaN-on-Diamond power semiconductor devices. This goal was achieved through extensive numerical simulations applied to device design, fabrication, and characterisation. The fabricated devices include conventional AlGaN/GaN HEMT design in circular and linear form with and without field plate engineering. The circular GaN-on-Diamond HEMTs with gate width of ~ 430 μm, gate length of 3 μm, gate-to-drain separation of 17 μm and source field plate length of 3 μm have shown breakdown voltage of ~ 1.1 kV. In this work a new concept of normally-off optically-controlled AlGaN/GaN-based power semiconductor device is proposed. A simulation study has been carried out in order to explore the DC characteristics, switching characteristics, breakdown voltage, and current gain of these novel devices. The typical structure comprises a 20 nm of undoped Al0.23Ga0.77N barrier layer, a 1.1 μm undoped-GaN buffer layer and a p-doped region (to locally deplete the electron channel and ensure a normally-off operation). The simulation study shows that the gain and the breakdown voltage of the device are highly dependent on the depth of the p-doped region. At a particular depth of the p-doped region of 500 nm the gain of the device is 970 (at light intensity of 7 W/cm2) and the breakdown voltage is ~ 350 V. The rise and fall times of the device is found to be 0.4 μsec and 0.3 μsec respectively. The simulation results show a significant potential of the proposed structure for high-frequency and high-power applications.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Electronic and Electrical Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.689328
Depositing User: Mr Turar Baltynov
Date Deposited: 11 Jul 2016 14:24
Last Modified: 12 Oct 2018 09:26
URI: http://etheses.whiterose.ac.uk/id/eprint/13522

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