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For example, these include the low and high growth temperature (LT-HT) In xGa 1−xAs step graded buffer and In xAl 1−xAs step graded buffer layer methods 18, 19, 20. In order to minimize defects caused by lattice mismatch, it is essential to employ a metamorphic growth technique. The dislocations have a negative impact on the physical properties of InAs due to electron-defect scattering. GaAs substrates are cheaper than InAs and InP substrates however, the lattice mismatch between GaAs and InAs is 7.2%, which leads to inevitable defects such as misfit dislocations (MDs) and threading dislocations (TDs). However, although the physical properties of InAs constitute a photodetector that is advantageous, manufacturing the detectors is difficult due to the cost of InAs wafers, which are more expensive than InP wafers.
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Due to the narrow band gap, InAs-based detectors can sense SWIR light that is longer than the cut-off wavelength of a conventional InGaAs photodetector. Indium arsenide (InAs), one of the III-V materials, has a high electron mobility of 30,000 cm 2/V Detectors that are of low-cost and fully cover the SWIR region are required.
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Also, the extended InGaAs and InGaAs/GaAsSb type-II quantum well photodetectors have been intensively studied, but so far cannot detect the full SWIR region 14, 15, 16, 17. HgCdTe (MCT) detectors are currently in widespread use in the SWIR range, but detectors are subject to high price and require an integrated cooling system 13.
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Such extensions could support a variety of applications, including pedestrian detection for advanced driver assistance systems (ADAS), and the identification of particulate matter in the air 12. Systems such as fiber optics, waveguides, emitters, and detectors are undergoing extensive research to find ways to extend performance from 1.7 μm to longer wavelengths in the SWIR range 6, 7, 8, 9, 10, 11. Recently, a ‘capacity crunch’ in this wavelength range was predicted based on the explosive increase in network traffic that is being driven by the development of the internet of things (IoT). Such devices are widely used in spectroscopy, night vision, gas sensing and telecommunications applications 1, 2, 3, 4, 5. Indium Gallium Arsenide (InGaAs) photodetectors on Indium Phosphide (InP) substrates are commonly used to detect the ‘classic’ short-wave infrared (SWIR) range of 1–1.7 μm.