p-i-n High-Speed Photodiodes for X-Ray and Infrared Imagers Fabricated by <i>In Situ</i>-Doped APCVD Germanium Homoepitaxy

Hunt, Charles E.; Carpenter, A.; Voss, Lars F.; Scott, Robert W. J.; Shao, Qinghui; Looker, Quinn; Anne, Garafalo,; Mistyuk, S; Durand, C E; Ankit, Kumar; Jean-Paul, Stroud,; Benthem, Klaus van

doi:10.1109/ted.2020.3006810

Cited by 5 publications

(6 citation statements)

References 15 publications

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“…The relatively low etch rates promote anisotropic etching and result in enhanced surface defects with 4-fold geometry. 1,18,20,24 The enhanced conductivity of the etchant due to the addition of MSP accelerates the oxidation reaction at the germanium surface and causes a more uniform etch front displayed by a more specular surface (cf Fig. 9c).…”

Section: Discussionmentioning

confidence: 99%

“…Recent advancements in homoepitaxially-grown germanium result in unprecedented low defect densities and incur interest in germanium as an alternative for next-generation backside imagers. 1 Compared to silicon, germanium is characterized by a smaller bandgap, improved X-ray and infrared photon absorption, and increased carrier mobilities. 1,2 These advantages favor germanium towards high throughput applications, such as high-speed hard X-ray imaging.…”

mentioning

confidence: 99%

“…1 Compared to silicon, germanium is characterized by a smaller bandgap, improved X-ray and infrared photon absorption, and increased carrier mobilities. 1,2 These advantages favor germanium towards high throughput applications, such as high-speed hard X-ray imaging. Appreciable absorption in the near-infrared regime, where silicon is essentially transparent, 1 makes germanium ideally suited for use in light detection and ranging (LiDAR) and photovoltaic systems.…”

mentioning

confidence: 99%

“…1,2 These advantages favor germanium towards high throughput applications, such as high-speed hard X-ray imaging. Appreciable absorption in the near-infrared regime, where silicon is essentially transparent, 1 makes germanium ideally suited for use in light detection and ranging (LiDAR) and photovoltaic systems. 3,4 The fabrication of backside imagers requires the removal of the substrate utilized for homoepitaxial growth, which is typically accomplished by selective etching.…”

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confidence: 99%

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Electrolytic Etching of Germanium Substrates with Hydrogen Peroxide

Wood,

van Buuren,

Guo

et al. 2023

J. Electrochem. Soc.

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Anodic electrolytic etching of germanium has been performed in hydrogen peroxide etchants with controlled external conditions. In-situ current and ex-situ etch-depths were measured and tracked with respect to etchant composition and stir rates. Gas bubbles formed during the etching process were found to cause non-uniformity in etch-current and surface quality. The effects were minimized in specific composition spaces. Quantitative analysis revealed a linear correlation of the number of electrons transferred during germanium oxidation with the number of surface atoms removed. Experimental results of 2.77 electrons/atom deviate significantly from 4 electrons/atom previously reported for silicon. The conclusion is that etching mechanisms for germanium are sufficiently different from those for silicon which invalidates the direct transfer of processing techniques between the two materials.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Electrolytic Etching of Germanium Substrates with Hydrogen Peroxide

Wood,

van Buuren,

Guo

et al. 2023

J. Electrochem. Soc.

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“…Germanium is a promising alternative for next-generation backside imagers since recent homoepitaxial growth has yielded extraordinarily low defect densities. [1][2][3][4] The intrinsic properties of germanium enable high-speed hard X-ray detection, and absorption in the near-infrared regime where silicon is essentially transparent. 1,5 Furthermore, germanium is suited as a potential foundational material in the growing field of quantum computing.…”

mentioning

confidence: 99%

Communication—Controlling Etching of Germanium through Surface Charge Manipulation

Wood,

Mitsyuk,

Brayfield

et al. 2024

J. Electrochem. Soc.

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Potassium hydroxide (KOH) aqueous solutions can effectively etch germanium. Etch rates were determined in an electrolytic etch cell. Electrically-isolated Ge wafers were subjected to an etch rate of 1.45±0.07 nm/min, increasing to 12.6±0.2 nm/min when grounded, 97±2 nm/min when biased at -0.9 V, and 138±2 nm/min with periodic biasing. Results suggest that previously reported limited etching in KOH is associated with the recombination of holes with electrons injected from the surface reaction. The results of this study demonstrate that changing the hole concentration through biasing is effective for controlling electrolytic etch rates, enabling future selective etching processes for germanium.

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