Development of fabrication processes toward integrated photonics in III-V semiconductors - GaP and GaN

  • Geraint P Gough

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Quantum technologies are taking the next step in their evolution, from not just using quantum mechanical effects, but manipulating them to gain a quantum supremacy over their classical counterparts. Areas that will benefit from this quantum advantage are communications and security, simulations and sensing. The area this quantum supremacy is greatly anticipated is computing, with the dawn of the quantum computer promising quicker algorithms.
Superconducting and trapped ion qubits have shown significant promise for a quantum computer. However, with the vast industrial infrastructure available for Si integrated circuits, along with Si photonics’ extensive history, a photonic quantum computer also shows promise. However, while Si does offer several useful properties for integrated photonics, it also has detrimental properties such as an indirect bandgap, centrosymmetric lattice structure and limited options for switching. Compound semiconductors offer beneficial properties like Si along with extra properties not available to Si (Pockels effect).
Simulations to find single mode waveguides in GaN and GaP, found waveguides with dimensions 1000 x 500 nm and 600 x 200 nm respectively. Single mode waveguides were found to avoid multimodal effects. With these waveguide dimensions, different switch designs were carried out where a MZI switch in a push-pull configuration was identified as the best design. Arm lengths of 8.4 mm and 11.4 mm for GaP and GaN respectively have a switching voltage of 4 V. The development of the fabrication process necessary to create these designs was done with the start of an etch matrix and lithographic tuning of designs. A novel angled cage etch was developed to create suspended GaN structures with singly and double clamped cantilevers created as well as experimenting with a conical cage. The goal is to create suspended photonic structures, the beginnings of which, a photonic nanobeam, are demonstrated.
Date of Award20 Jul 2021
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorJorge Barreto (Supervisor)

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