A study of passivation, dark current and 1/f noise in mid-wave infrared HgCdTe photovoltaic detectors

Ryan Westerhout

    Research output: ThesisDoctoral Thesis

    665 Downloads (Pure)

    Abstract

    [Truncated abstract] There are many areas in which the detection of infrared (IR) radiation plays a crucial role, such as astronomy, biomedical diagnostics, and defence and security applications. Photodiodes are currently the most widely used detection devices as they provide low power, high pixel density, fast response times and a more uniform spatial response across the focal plane imaging array. For high quality IR detectors the material of choice is an alloy of mercury telluride and cadmium telluride (HgCdTe). This is due to the desirable properties of HgCdTe, in particular the variable cutoff wavelength from 0.7 to 25 μm and lattice-matching across the entire alloy range. However, HgCdTe material is difficult to work with and uniformity and yield are still unresolved issues. At The University of Western Australia (UWA), HgCdTe photodiode passivation is a two step process, consisting of a layer of Molecular beam epitaxy (MBE) deposited CdTe and a thermally evaporated layer of ZnS. During investigation of these devices, the ZnS layer can also be used as an insulator for a gate electrode to control the surface dark current characteristics of the p-n junction. When measuring the 1/f noise characteristics of these diodes the insulating properties of the ZnS degrade with time, eventually resulting in the diodes no longer being controlled by the gate electrode. It is proposed that SiN is a suitable replacement for ZnS as the insulating layer for gate controlled HgCdTe photodiodes. SiN has previously been used in microelectronics as a protective layer against mobile ions and other external contaminants in Si-SiO2 microelectronic technology...
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2013

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