Plasma-enhanced atomic layer deposited SiO2 enables positive thin film charge and surface recombination velocity of 1.3 cm/s on germanium

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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2023-05-09
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en
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Applied Physics Letters, Volume 122, issue 19
Abstract
The excellent field-effect passivation provided by aluminum oxide (Al2O3) on germanium surfaces relies on the high negative fixed charge present in the film. However, in many applications, a neutral or a positive charge would be preferred. Here, we investigate the surface passivation performance and the charge polarity of plasma-enhanced atomic layer deposited (PEALD) silicon oxide (SiO2) on Ge. The results show that even a 3 nm thick PEALD SiO2 provides a positive charge density (Qtot, ∼2.6 × 1011 cm−2) and a relatively good surface passivation (maximum surface recombination velocity SRVmax ∼16 cm/s). When the SiO2 thin film is capped with an ALD Al2O3 layer, the surface passivation improves further and a low midgap interface defect density (Dit) of ∼1 × 1011 eV−1 cm−2 is achieved. By varying the SiO2 thickness under the Al2O3 capping, it is possible to control the Qtot from virtually neutral (∼2.8 × 1010 cm−2) to moderately positive (∼8.5 × 1011 cm−2) values. Consequently, an excellent SRVmax as low as 1.3 cm/s is obtained using optimized SiO2/Al2O3 layer thicknesses. Finally, the origin of the positive charge as well as the interface defects related to PEALD SiO2 are discussed. © 2023 Author(s).
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Liu, H, Pasanen, T, Leiviskä, O, Isometsä, J, Fung, J, Yli-Koski, M, Miettinen, M, Laukkanen, P, Vähänissi, V & Savin, H 2023, ' Plasma-enhanced atomic layer deposited SiO2 enables positive thin film charge and surface recombination velocity of 1.3 cm/s on germanium ', Applied Physics Letters, vol. 122, no. 19, 191602 . https://doi.org/10.1063/5.0152652