Active matrix single-photon technologies on GaAs

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The proposed research addresses the need for technologies able to detect single photons at infrared wavelengths, especially in the short-wave (SWIR) and mid-wave (MWIR) infrared. A number of electronic devices based on quantum phenomena, the so called "first" generation of quantum technology, are widespread and used every day for a number of applications. Research has recently shown that some quantum phenomena formerly considered mere scientific curiosities, such as particle entanglement, could have many interesting applications. A "second" generation of quantum technologies is therefore the subject of intense research effort, given their great potential for commercialisation. With regard to the imaging field, new advances in quantum technology include imaging of light in flight and detection of objects hidden behind corners. Such applications rely on cameras where each pixel is sensitive enough to detect single photons, and it consists of a silicon single photon avalanche detector (SPAD) achieved on the same chip as the addressing circuitry required. Silicon offers a commercially mature platform for SPAD-based cameras, but unfortunately on this material platform operation is limited to visible wavelengths. Imaging arrays of SPADs working at infrared wavelengths, not currently available, are highly desirable as they would unlock further applications in the field of industry asset management, biomedical imaging and environmental monitoring. The micro-system technology (MST) group at the University of Glasgow has pioneered MWIR imagers integrating indium antimonide (InSb) photodiodes (PDs) with gallium arsenide (GaAs) metal semiconductor field effect transistors (MESFETs) for addressing. Such imagers are able to operate at room temperature and as such they offer a robust and low-cost alternative to available devices in the MWIR wavelength range, which require cooling. Furthermore, most available MWIR imagers are based on hybridised technologies where PDs and addressing circuitry are attained on separate chips and then combined through flip-chip bonding, a costly and low-yield technique. Compound Semiconductor Technologies (CST) Global Ltd, leading the proposed research, will take the MWIR monolithic technology pioneered by Glasgow University and develop it into a robust manufacturing line aimed at commercialisation. The technology platform is extendable to provide functions at other wavelengths and in single-photon counting by appropriate selection of photo-active semiconductors. Gas Sensing Solutions (GSS) Ltd, a long-standing partner of CST Global Ltd and GU will lead the development of new materials to achieve SPADs at infrared wavelengths, supported by design and prototyping at GU.