Novel CMOS Devices for High Energy Physics and Medical Applications

HEP experiments at particle colliders probe our understanding of the structure and dynamics of matter. In order to advance the field, the accelerator systems are periodically upgraded to higher energies and luminosities. Experiments have to keep up, by improving their detector instrumentation. Silicon pixel detectors play a critical role in HEP experiments. Thanks to their excellent position resolution, compactness, speed and radiation hardness, they enable particle track reconstruction in high radiation environments like hadron colliders. In turn, their performance allows excellent track impact parameter resolution, a key ingredient for secondary vertex identification and jet b-tagging. Currently the state of the art in HEP are hybrid pixel detectors consisting of a segmented sensor, in which each pixel is connected to a readout channel of an ASIC through a complicated, and expensive, technique called bump bonding. An alternative approach to hybrid pixel devices are monolithic detectors, which combine the particle sensing and the signal processing elements in the same substrate. These kind of detectors developed in the CMOS process are widely used in industrial applications for light detection and have been employed for the first time in a HEP experiment for the STAR tracker at RHIC. However, it is only relatively recently that DMAPS have been proposed which could sustain extreme radiation doses and large particle rates. In this thesis two prototypes of DMAPS developed in the HV-CMOS technology are investigated as pixel devices for the outer layers of the future upgrade of the ATLAS tracker, which is located in the LHC at CERN. Besides the employment in HEP experiments, this technology has also potential for the development of cost effective photon detectors for medical applications. Two device concepts are investigated for this purpose: HV-CMOS pixel detectors for the measurement of soft X-ray photons and APD for the detection of NIR photons.