15 February 2012 Development of high-transmittance back-illuminated silicon-on-sapphire substrates thinned below 25 micrometers and bonded to fused silica for high quantum efficiency and high resolution avalanche photodiode imaging arrays
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Abstract
There is a growing need in scientific and industrial applications for dual-mode, passive and active 2D and 3D LADAR imaging methods. To fill this need, solid-state, single photon sensitive silicon avalanche photodiode (APD) detector arrays offer high sensitivity and the possibility to operate with wide dynamic range in dual linear and Geiger-mode for passive and active imaging. To support the fabrication of large scale, high quantum efficiency and high resolution silicon avalanche photodiode arrays and other advanced solid-state optoelectronics, a novel, high transmittance, backilluminated silicon-on-sapphire substrate has been developed incorporating a single crystal, epitaxially grown aluminum nitride (AlN) antireflective layer between silicon and R-plane sapphire, that provides refractive index matching to improve the optical transmittance into silicon from sapphire. A one quarter wavelength magnesium fluoride antireflective layer deposited on the back-side of the sapphire improves optical transmittance from the ambient into the sapphire. The magnesium fluoride plane of the Si-(AlN)-sapphire substrate is bonded to a fused silica wafer that provides mechanical support, allowing the sapphire to be thinned below 25 micrometers to improve back-illuminated optical transmittance, while suppressing indirect optical crosstalk from APD emitted light undergoing reflections in the sapphire, to enable high quantum efficiency and high resolution detector arrays.
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Alvin G. Stern, Alvin G. Stern, } "Development of high-transmittance back-illuminated silicon-on-sapphire substrates thinned below 25 micrometers and bonded to fused silica for high quantum efficiency and high resolution avalanche photodiode imaging arrays", Proc. SPIE 8298, Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII, 82980K (15 February 2012); doi: 10.1117/12.908983; https://doi.org/10.1117/12.908983
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