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

Author:

Liu Hanchen1ORCID,Pasanen Toni P.1ORCID,Leiviskä Oskari1ORCID,Isometsä Joonas1ORCID,Fung Tsun Hang1ORCID,Yli-Koski Marko1,Miettinen Mikko2ORCID,Laukkanen Pekka2ORCID,Vähänissi Ville1ORCID,Savin Hele1ORCID

Affiliation:

1. Aalto University, Department of Electronics and Nanoengineering 1 , Tietotie 3, 02150 Espoo, Finland

2. Department of Physics and Astronomy, University of Turku 2 , FI-20014 Turku, Finland

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.

Funder

Horizon 2020 Framework Programme

Business Finland

Academy of Finland

Finnish Research Impact Foundation

Publisher

AIP Publishing

Subject

Physics and Astronomy (miscellaneous)

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