Electronic and optoelectronic devices are crucial in modern society, facilitating communication, providing worldwide access to information, and playing a significant role in medicine, imaging technology, and particle detection. Researchers are increasingly exploring materials and design strategies to meet the growing demand for detectors with better performance, such as high-speed operation, small size, low cost, compatibility with CMOS technology, high signal-to-noise ratio, wide spectral response, and radiation hardness. Graphene/silicon (Gr/Si) Schottky photodiodes are promising candidates for high-speed broadband detection. Due to the high carrier mobility, broadband light absorption, and high conductivity of graphene, the collection efficiency of photogenerated carriers can be enhanced, but careful design and materials of the photodiode structure are required to achieve high-speed operation. This research includes the design, simulation, fabrication, and characterisation of a high-speed Gr/Si Schottky photodiode built on the principles of impact avalanche ionisation. Circular geometry plays a pivotal role in ensuring uniform electric field enhancement along the perimeter of the 1260 ãμmã^2 active area via circular electrodes, thereby optimising carrier collection efficiency. Characterisation is facilitated by an automated table-top scanning photocurrent microscopy, capable of performing a 4D-scan including laser power, applied voltage, and two spatial dimensions. Photocurrent mapping reveals uniformity across the Gr/Si area. The device shows an ultrafast response time of 4 ns at a voltage of 0.1 V, a noticeable improvement over recent studies. These results show the potential applications of this design, providing cost-effective, high-speed operation, broadband capability, and a compact photodiode. This research introduces an adaptable microscope setup that has a tunable femtosecond laser source (330 - 16,000 nm). Consequently, it enables two-photon absorption (TPA) processes. TPA is an emerging characterisation technique that provides voxel-based 3D spatial resolution and deep penetration. This TPA setup overcomes the limitations of traditional tabletop TPA setups limited to 1550 nm. Extending the applicability of TPA to materials beyond silicon. TPA technique is used to examine diamond and silicon detectors by mapping photocurrent along depth and examining photogenerated carrier inhomogeneity using sub-micron XYZ spatial scans. This setup excels as a detector characterisation tool, offering exceptional spatial resolution, flexibility, automation, and wide bandwidth. It applies to various detectors, including low-gain avalanche photodiode (LGAD), 2D, and 3D diamond detectors.
Date of Award | 1 Aug 2024 |
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Original language | English |
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Awarding Institution | - The University of Manchester
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Supervisor | David Binks (Supervisor) & Patrick Parkinson (Supervisor) |
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- Avalanche
- Diamond
- Responsivity
- Photocurrent Mapping
- Two Photon Absorption
- Schottky
- Simulation
- Graphene
- Microscopy
- Photocurrent
- Photo- and Particle Detectors
Optimisation of Photo- and Particle Detectors using Ultrafast Scanning Photocurrent Microscopy
Al Amairi, N. (Author). 1 Aug 2024
Student thesis: Phd