A1 Journal article (refereed)
Silicon Surface Passivation by ALD-Ga2O3 : Thermal vs. Plasma-Enhanced Atomic Layer Deposition (2020)


Hiller, D., Julin, J., Chnani, A., & Strehle, S. (2020). Silicon Surface Passivation by ALD-Ga2O3 : Thermal vs. Plasma-Enhanced Atomic Layer Deposition. IEEE Journal of Photovoltaics, 10(4), 959-968. https://doi.org/10.1109/JPHOTOV.2020.2989201


JYU authors or editors


Publication details

All authors or editors: Hiller, Danie; Julin, Jaakko; Chnani, Ahmed; Strehle, Steffen

Journal or series: IEEE Journal of Photovoltaics

ISSN: 2156-3381

eISSN: 2156-3403

Publication year: 2020

Volume: 10

Issue number: 4

Pages range: 959-968

Publisher: IEEE

Publication country: United States

Publication language: English

DOI: https://doi.org/10.1109/JPHOTOV.2020.2989201

Publication open access: Not open

Publication channel open access:


Abstract

Silicon surface passivation by gallium oxide (Ga 2 O 3 ) thin films deposited by thermal- and plasma-enhanced atomic layer deposition (ALD) over a broad temperature range from 75 °C to 350 °C is investigated. In addition, the role of oxidant (O 3 or O-plasma) pulse lengths insufficient for saturated ALD-growth is studied. The material properties are analyzed including the quantification of the incorporated hydrogen. We find that oxidant dose pulses insufficient for saturation provide for both ALD methods generally better surface passivation. Furthermore, different Si surface pretreatments are compared (HF-last, chemically grown oxide, and thermal tunnel oxide). In contrast to previous reports, the annealing time to activate the surface passivation is found to be significantly shorter. The best surface saturation current densities (J 0s ) or surface recombination velocities (S eff ) are 6 and 9 fA/cm² or 0.6 and 1.5 cm/s for n- and p-type Si, respectively. We correlate the surface passivation with the negative fixed charge density (Q fix ; field-effect passivation) and the interface defect density (D it ; chemical passivation). It turns out that a high Q fix is present, irrespective of the utilized ALD-method, deposition temperature, or postannealing, whereas low D it is only achieved for plasma-enhanced ALD at low temperatures. A critical H-density of ∼1016 cm−2 is identified as a necessary but not sufficient condition for excellent surface passivation. Finally, contact resistivities are measured to investigate the possibility of using ALD-Ga 2 O 3 as passivating contact material. In order to understand the current-voltage measurements, the energetic positions of the band edges and the Fermi level are determined by ultraviolet photoelectron spectroscopy and Kelvin probe.


Free keywords: atomic layer deposition (ALD); gallium oxide (Ga2O3); hydrogen; silicon surface passivation


Contributing organizations


Ministry reporting: Yes

Reporting Year: 2020

JUFO rating: 1


Last updated on 2021-07-07 at 21:30