The Microelectronics Research Group (MRG) at The University of Western Australia is a key partner of the Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems. In this presentation, an overview of ongoing research will be given with an emphasis on the flagship research activities of MCT-based imaging arrays and Microelectromechanical Systems (MEMS). The MCT research and development utilise a vertically integrated capability from semiconductor material growth, through device modelling and design, to focal-plane-array fabrication and packaging. In support of the detector array capability, fully integrated MEMS technology can be used to further enhance the sensor device performance through the focal plane integration of tunable filters for spectral classification and infrared spectroscopy. The combination of high-performance detector designs and tunable spectral filters provides a major differentiator for military imaging systems, particularly for those operating in complex and degraded environments. This talk will highlight several research activities that are highly relevant to defence applications including metamaterial enhanced infrared detectors, and the fabrication of infra-red focal plane arrays on flexible substrates. For the MEMS technology, both wideband and narrowband tunable spectral filters will be discussed for multispectral imaging in the SWIR, MWIR and LWIR bands, and for hyperspectral imaging and spectroscopy. Considerations on future research activities and technology trends will be presented including opportunities for the rapid development of high-performance and spectrally adaptive low SWaP sensing systems for enhanced detection and discrimination of partially concealed or camouflaged targets in cluttered backgrounds.
The Microelectronics Research Group (MRG) at UWA has been developing its capabilities in the field of infrared materials and devices since 1989 and is the only HgCdTe research centre in Australia. In this paper, we report on the various HgCdTe based technologies being researched at UWA to enhance their capabilities for demanding applications such as heteroepitaxy-enabled low-cost, large array size, and high-performance HgCdTe IR FPAs, and ultra-high Quantum Efficiency (QE) HgCdTe detectors for squeezed-light applications.
High performance infrared (IR) sensing and imaging systems require IR optoelectronic detectors that have a high signal-to-noise ratio (SNR) and a fast response time, and that can be readily hybridised to CMOS read-out integrated circuits (ROICs). From a device point of view, this translates to p-n junction photovoltaic detectors based on narrow bandgap semiconductors with a high quantum efficiency (signal) and low dark current (noise). These requirements limit the choice of possible semiconductors to those having an appropriate bandgap that matches the wavelength band of interest combined with a high optical absorption coefficient and a long minority carrier diffusion length, which corresponds to a large mobility-lifetime product for photogenerated minority carriers. Technological constraints and modern clean-room fabrication processes necessitate that IR detector technologies are generally based on thin-film narrow bandgap semiconductors that have been epitaxially grown on lattice-matched wider bandgap IR-transparent substrates. The basic semiconductor material properties have led to InGaAs (in the SWIR up to 1.7 microns), InSb (in the MWIR up to 5 microns), and HgCdTe (in the eSWIR, MWIR and LWIR wavelength bands) being the dominant IR detector technologies for high performance applications. In this paper, the current technological limitations of HgCdTe-based technologies will be discussed with a view towards developing future pathways for the development of next-generation IR imaging arrays having the features of larger imaging array format and smaller pixel pitch, higher pixel yield and operability, higher quantum efficiency (QE), higher operating temperature (HOT), and dramatically lower per-unit cost.
HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs
of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched
CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective
alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching.
In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material
system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar
nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent
flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia
(UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn
structures.
A theoretical calculation result of Hg1-xCdxTe (x=0.3) avalanche photodiodes (APDs) based on PIN structure is
obtained in the paper, which has a ratio of ionization factor k=0.06. The energy dispersion factor and the threshold
energy are acquired according to the parameters of material. And the gain, as well as the breakdown voltage, is obtained.
The composition, thickness, doping level is calculated theoretically to get an optimized APD device.
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