Currently, the testing procedure for 3D Hall sensors at the MUSIC lab is time-consuming, labour intensive, and is susceptible to systematic errors. There is a need for an automated, accurate, and repeatable test setup for 3D magnetic sensor characterisation. That is why the objective of this thesis is to develop a control interface that allows users to define arbitrary magnetic field vectors and perform 3D magnetic field sweeps on a Hall sensor placed in a 3D Helmholtz coil. The development was performed in three stages: calibration of a 3D Helmholtz coil, development of a 3D magnetic field sweeping script, and validation of the system by benchmarking measurements from two commercially available 3D Hall sensors against known magnetic fields. The 3D Helmholtz coil was successfully calibrated, finding that the generated magnetic field strength of 2.87mT corresponds to the maximum relative uncertainty of 2%. A LabVIEW script was developed, enabling users to generate 3D static magnetic field vectors and 3D magnetic field sweeps with definable orientation, resolution and strength. Lastly, the system was validated using two commercial Hall sensors, confirming its stability and accuracy for testing other Hall sensors. This system can be used for repeatable magnetic sensor evaluation in research, with a versatility that can benefit various sensor configurations.

As novel three dimensional Hall sensors are being developed, it is important to be able to demonstrate their working principles and applications to other researchers and potential investors. One such application is seen in joysticks, which are more durable and reliable when they are made with Hall sensors compared to traditional potentiometer joysticks. In order to develop the joystick, readout mechanisms for multiple commercial Hall sensors are developed first. A joystick design configuration and permanent magnet are selected based on requirements and magnetic field simulations. The joystick is 3D printed and a demonstration screen showing the position of the stick and a moving ball is developed. The joystick has a delay of 9 ms, a maximum pitch of 61°, a resolution higher than 1° and an average error of 2.4° for the pitch and 1.59° for the rotation angle. However, this error may be due to the way the angle was physically measured, rather than errors in the measured magnetic field. Overall, the resulting joystick prototype functions more than sufficiently as a demonstrator.

This thesis presents a comprehensive study on the fabrication and characterization of a buried invertedpyramid Hall sensor realized using pure-boron LPCVD. Conventional inverted-pyramid Hall sensors typically suffer from high residual offset and elevated flicker noise, effects that are often attributed to charge trapping at the passivation surface. Introducing a buried sensing layer is an effective strategy to mitigate these surface-related disturbances.
Motivated by this concept, a p+ layer was integrated into the pyramid Hall sensor architecture. Pureboron LPCVD was employed to form the required ultra-shallow junction, taking advantage of the absence of channeling and transient-enhanced diffusion effects commonly observed in ion-implanted boron. To minimize interference from the junction field effect, the boron deposition process was modeled and simulated using Synopsys Sentaurus. Based on these results, a one-minute LPCVD boron process was implemented to form the p+–n junction above the active region.
The fabricated sensors exhibit an equivalent magnetic residual offset ranging from 7.5 μT to 710 μT, with the buried sensor showing a lower residual offset in most modes. The sensor demonstrates a thermal noise floor of approximately 1 μT/√Hz at a 1.26 V supply. Flicker-noise analysis using the Hooge model reveals that the buried inverted-pyramid Hall sensors exhibit a lower αH/N and a reduced corner frequency compared to conventional devices, indicating a possible improvement in low-frequency noise performance.

This thesis presents a complete study on the growth, fabrication, and characterization of Gallium Arsenide (GaAs) layers on Si(111) substrates using Metal-Organic Vapour Phase Epitaxy (MOVPE) for potential application in 3D Hall effect sensors. The (111) orientation was selected due to its compatibility with pyramid-shaped Hall sensor architectures and its reduced likelihood of antiphase domain formation compared to Si(100). GaAs is selected as the active material due to its high electron mobility and relatively small lattice mismatch with silicon, which together can enhance sensor sensitivity, signal to noise ratio and thermal stability.

A two-step growth approach was employed, consisting of a low temperature nucleation layer and a high temperature main layer. Systematic variation of temperature, V/III ratio, and growth rate revealed that smoother and more crystalline layers were obtained at higher growth rates and moderate precursor ratios. The optimal conditions produced continuous, well coalesced GaAs films with high crystalline quality at par with literature.

A major outcome of this work is the development of a complete, reproducible microfabrication flow for GaAs on Si devices. Enabling the fabrication of diodes, MOS capacitors, four-point probes and Hall structures, that allow for direct electrical characterisation of the grown layers.

Electrical performance was evaluated through micro-fabricated test structures, providing insights into carrier resistivity, contact resistance, carrier concentration and interface state density. While contact resistivity limited some analyses, the results demonstrate successful electrical integration of the grown material.

Future work will focus on refining the main layer growth conditions, optimising ohmic contacts, etching for GaAs and Si interfaces and completing Hall effect measurements under magnetic fields to fully assess the material’s sensing performance for Hall devices.

CMOS Hall sensors consist of current-biased n-well plates that output magnetic-field dependent voltages. Offsets due to n-well inhomogeneity can then be suppressed by the spinning-current technique, which involves periodically rotating the direction of the biasing current and averaging the resulting output voltages. However, its effectiveness is limited by the JFET effect, which refers to the formation of a depletion region between the n-well and the p-type substrate due to the voltage drop across the n-well. This depletion region modulates the n-well resistance, and so is also a source of residual offset.

In this work, a CMOS Hall sensor is reported which employs voltage biasing and reads out the short-circuit Hall current. Compared to current biasing, this stabilizes the voltage drop across the n-well and significantly reduces the offset due to the JFET effect. Implemented in a standard 180nm CMOS process, the resulting sensor achieves a 3σ offset of 1.1μT with a noise floor of 60nT/√Hz. Compared to the state-of-the-art, these results represent a 3x reduction in offset, and a 5x improvement in resolution.

Thermoelectric generators (TEGs) are critical in environments where alternative energy harvesting methods are necessary, such as space exploration. This thesis investigates using a two-dimensional hole gas (2DHG) as a p-type material within a Gallium Nitride (GaN) based TEG. This study focuses on determining the thermoelectric performance of the 2DHG by measuring the Seebeck coefficient, electrical conductivity, and power factor for extremely cold environments.

This work introduces a novel simulation method used to evaluate different structures to find the optimal hole densities for maximizing the power factor (PF) of the 2DHG. A structure was realized, and its thermoelectric properties were experimentally assessed. Key results, including a Seebeck coefficient of 100 − 200 μV /∆K, a sheet resistance of 70 − 120 kΩ , and a resulting Power Factor (PF) of 60 − 100 μW m−1K−2, are measured over an extremely low-temperature range of 50 - 300 Kelvin and discussed for future applications.

These results demonstrate that GaN-based TEGs can significantly broaden the temperature range and improve the performance of TEGs in extreme conditions. These findings pave the way for more efficient thermoelectric systems, with potential applications in aerospace, deep-space missions, and other challenging environments.

The goal of this thesis is to develop a ROS package that facilitates the control and navigation of a Duckiebot robot. With the rise of robot swarms the need for autonomous charging system for robots is increasing. An implementation for decentralised autonomous behaviour for a Duckiebot for a wireless charging system in a Duckietown environment is discussed. The devised system is divided among three different modules and is implemented in ROS:
• An image recognition module;
• A navigation module;
• A motion control module;
The image recognition module uses linear image processing techniques and YOLO object detection in order to detect objects in images from the robots front facing camera. It detects traffic lights and road markings in order to tell the robot where to go.

The navigation module uses odometry to keep track of the robots current position. The odometry is reset in order to maintain accuracy. When the battery of the robot reaches a certain point the robot will decide to
charge. It will then initiate path finding using Lee’s algorithm in order to find a path to a charging park.

Finally the motion control processes all the information in order to drive the wheels of the robot.
The system is thought to be able to navigate to a charging station, charge and then leave the charging station using the designed ROS package.