Resonant cavity detectors and their materials, for spectroscopic chemical detection

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The project is aiming to create and study infrared detectors for spectroscopic detection, primarily aimed at substances that require more sensitive detectors than are currently available. The detectors will be resonant cavity enhanced (a mirror is placed either side of the active layer) to improve spectral selectivity. These detectors are still in the research realm, with their demonstration yet to be achieved in some important wavelength ranges, and some open questions regarding their operation and the reconciliation of theory and experimental data. For example one important target of the project is to experimentally prove that the maximum sensitivity of resonant cavity detectors can be above the theoretical limit for standard detectors, as it is predicted to be. This has not yet been achieved. If the project were condense to two questions they would be "can resonant cavity detectors be achieved in the short and long wave infrared" and "can their measured performance be fully reconciled with their theory, or does this need modifying". The detectors will be modelled and designed by the student. They will grow it by molecular beam epitaxy (MBE) using InGaAsSb absorbers for short wave detectors (1.4 to 3.0 micro meters), InAsSb or super lattice absorbers for mid wave detectors (3 to 5 micro meters) and super lattice absorbers for long wave detectors (8 to 12micro meters). They will process in our cleanroom and characterise thein the lab for leakage current, spectral response and quantum efficiency in particular. The student will complete all this work, publishing their result. We expect this PhD to advance understanding in the materials used and the physical understanding of resonant cavity detectors, in particular their leakage current mechanisms. This will also by extension improve understanding of conventional detector device physics, which the resonant cavity design is attempting to push towards a limit.EPSRC research area: photonic materials and devices