Pixel detector with exotic sensors: device characterisation, analysis, and application

Lombigit, Lojius (2024) Pixel detector with exotic sensors: device characterisation, analysis, and application. PhD thesis, University of Glasgow.

Abstract

The detection of charged particles is an integral part of several scientific endeavours. To detect a charge particle, it must interact with a sensing volume and produce charges within it that can be read out. In hybrid pixel sensor, the sensor and readout electronics can be optimised separately, and this property makes them highly desirable for future applications.

University of Glasgow and Micron Semiconductor Ltd collaboration produces 50 µm thick LGAD and a 250 µm thick iLGAD sensors. The LGADs are envisaged as fast-timing detectors for particle physics experiments, while the iLGADs were developed as a technological solution to solve issues with the low fill factor in the conventional LGAD. These detectors are produced as pad detectors of various pixel sizes and doping concentrations for testing. The pixelated version of the 250 µm thick iLGAD and an earlier iteration of a 200 µm LGAD are bonded to Timepix3 readout ASICs as one-of-a-kind hybrid pixel detector prototypes. In addition to these detectors, the University of Glasgow also produced hybrid pixel detectors with high-Z sensors.

The electrical properties of the (i)LGAD pad detectors are explored via IV and CV measurements. Some LGAD pad detectors are also evaluated for their gain using the TCT with a 1040nm infrared laser source. The doping concentration in the multiplication region dictates the electrical characteristics of (i)LGADs. The 50 µm thick LGADs achieve full depletion at voltages between 26V to 31V. Breakdown voltages were 5 to 9 times higher than full depletion voltage, indicating a wide dynamic range for operation. The JTE width or, collectively, the device’s active area restricts the achievable gain and fill factor in the 50 µm thick LGAD. The 1.0mm × 1.0mm LGAD achieves a 6.75 gain at 30 ◦C, with a 74% increase in gain for a 50 ◦C temperature drop.

The hybrid pixel detectors with (i)LGAD sensors are calibrated for energy and corrected for time-walk with XRFs and γ-ray sources. Subsequently, their pixel responses and signal gains are investigated with a micro-focused synchrotron beam at Beamline B16, Diamond Light Source. No signal gain was observed in the hybrid pixel detector with 55 µm pitch LGAD, but this is expected and fully understood—however, the 110 µm pitch variant performed with a limited fill factor as expected, with a gain of around 5 at −350V bias voltage. The iLGAD is a viable solution to overcome the low-fill factor of an LGAD. A gain of around 5 at 250V bias voltage with a fill factor of more than 80% was obtained in the hybrid pixel detector with 55 µm pitch iLGAD.

The thesis also discussed the application of a hybrid pixel detector with a high-Z sensor as a single-layer Compton camera. Proof of concept was demonstrated in a very thin (1mm thick), 55 µm pitch CdTe bonded to a Timepix3 readout ASIC. Despite limited data, an image depicting the origin of a gamma-ray source was fully reconstructed just by utilising the Compton scattering kinematics.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Maneuski, Dr. Dima and O’Shea, Professor Valentine
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84736
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 05 Dec 2024 10:19
• Last Modified: 10 Dec 2024 09:50
• Thesis DOI: 10.5525/gla.thesis.84736
• URI: https://theses.gla.ac.uk/id/eprint/84736