A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Surface Passivation of Germanium with ALD Al2O3: Impact of Composition and Crystallinity of GeOx Interlayer
Tekijät: Isometsä Joonas, Jahanshah Rad Zahra, Fung Tsun H., Liu Hanchen, Lehtiö Juha-Pekka, Pasanen Toni P., Leiviskä Oskari, Miettinen Mikko, Laukkanen Pekka, Kokko Kalevi, Savin Hele, Vähänissi Ville
Kustantaja: MDPI
Julkaisuvuosi: 2023
Journal: Crystals
Tietokannassa oleva lehden nimi: CRYSTALS
Lehden akronyymi: CRYSTALS
Artikkelin numero: 667
Vuosikerta: 13
Numero: 4
Sivujen määrä: 10
eISSN: 2073-4352
DOI: https://doi.org/10.3390/cryst13040667
Verkko-osoite: https://doi.org/10.3390/cryst13040667
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/179815269
Germanium is an excellent material candidate for various applications, such as field effect transistors and radiation detectors/multijunction solar cells, due to its high carrier mobilities and narrow bandgap, respectively. However, the efficient passivation of germanium surfaces remains challenging. Recently, the most promising results have been achieved with atomic-layer-deposited (ALD) Al2O3, but the obtainable surface recombination velocity (SRV) has been very sensitive to the surface state prior to deposition. Based on X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED), we show here that the poor SRV obtained with the combination of HF and DIW surface cleaning and ALD Al2O3 results from a Ge suboxide interlayer (GeOx, x < 2) with compromised quality. Nevertheless, our results also demonstrate that both the composition and crystallinity of this oxide layer can be improved with a combination of low-temperature heating and a 300-Langmuir controlled oxidation in an ultrahigh vacuum (LT-UHV treatment). This results in a reduction in the interface defect density (D-it), allowing us to reach SRV values as low as 10 cm/s. Being compatible with most device processes due to the low thermal budget, the LT-UHV treatment could be easily integrated into many future devices and applications.
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