Ge interface engineering using ultra-thin La2O3 and Y2O3 films: A study into the effect of deposition temperature

Mitrovic, IZ ORCID: 0000-0003-4816-8905, Althobaiti, M, Weerakkody, AD, Dhanak, VR, Linhart, WM, Veal, TD ORCID: 0000-0002-0610-5626, Sedghi, N ORCID: 0000-0002-2004-6159, Hall, S ORCID: 0000-0001-8387-1036, Chalker, PR ORCID: 0000-0002-2295-6332, Tsoutsou, D
et al (show 1 more authors) (2014) Ge interface engineering using ultra-thin La2O3 and Y2O3 films: A study into the effect of deposition temperature. Journal of Applied Physics, 115 (11).

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A study into the optimal deposition temperature for ultra-thin La2O3/Ge and Y2O3/Ge gate stacks has been conducted in this paper with the aim to tailor the interfacial layer for effective passivation of the Ge interface. A detailed comparison between the two lanthanide oxides (La2O3 and Y2O3) in terms of band line-up, interfacial features, and reactivity to Ge using medium energy ion scattering, vacuum ultra-violet variable angle spectroscopic ellipsometry (VUV-VASE), X-ray photoelectron spectroscopy, and X-ray diffraction is shown. La2O3 has been found to be more reactive to Ge than Y2O3, forming LaGeOx and a Ge sub-oxide at the interface for all deposition temperature studied, in the range from 44 °C to 400 °C. In contrast, Y2O3/Ge deposited at 400 °C allows for an ultra-thin GeO2 layer at the interface, which can be eliminated during annealing at temperatures higher than 525 °C leaving a pristine YGeOx/Ge interface. The Y2O3/Ge gate stack deposited at lower temperature shows a sub-band gap absorption feature fitted to an Urbach tail of energy 1.1 eV. The latter correlates to a sub-stoichiometric germanium oxide layer at the interface. The optical band gap for the Y2O3/Ge stacks has been estimated to be 5.7 ± 0.1 eV from Tauc-Lorentz modelling of VUV-VASE experimental data. For the optimal deposition temperature (400 °C), the Y2O3/Ge stack exhibits a higher conduction band offset (>2.3 eV) than the La2O3/Ge (∼2 eV), has a larger band gap (by about 0.3 eV), a germanium sub-oxide free interface, and leakage current (∼10−7 A/cm2 at 1 V) five orders of magnitude lower than the respective La2O3/Ge stack. Our study strongly points to the superiority of the Y2O3/Ge system for germanium interface engineering to achieve high performance Ge Complementary Metal Oxide Semiconductor technology.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 28 Apr 2016 13:26
Last Modified: 09 Jan 2021 08:30
DOI: 10.1063/1.4868091
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