GaN Distributed Bragg Reflector Cavities for Sensing Applications

  • Simeng Jia

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


The purpose of this thesis is to design Distributed Bragg Reflector cavities with integrated grating couplers connected by integrated waveguides. These structures can be used as sensors based on changes in resonance wavelengths when analytes are present in the cavity. The theory of grating couplers is introduced, and this is followed by detailed Finite Difference Time Domain modelling of the structures. Distributed Bragg Reflector cavities are then studied and the effect of using multi-mode waveguides on their performance is investigated.
This thesis studies two GaN based platforms, the first is a multi-moded GaN on sapphire platform. Based on the results of simulation optimisation, a chip is fabricated using a low-cost nanofabrication technique known as Displacement Talbot Lithography technology. This is a novel fabrication method that can perform wafer scale nanofabrication, but with the restriction that all periodic structures must have the same period and etch depth. Simulation and experimental results are compared and good agreement is shown. The structure also shows good potential for sensor applications. The second is a thinner GaN-AlN on sapphire platform. The devices are fabricated by Electron Beam Lithography technology, which allows more flexible and precise selection of structural parameters. Since a thinner gallium nitride layer is used and waveguides in this structure can realise single-mode transmission, and the results show will improve the performance of the sensor.
Date of Award26 Nov 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorMartin J Cryan (Supervisor) & John G Rarity (Supervisor)

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