Ge interface engineering using ultra-thin La{sub 2}O{sub 3} and Y{sub 2}O{sub 3} films: A study into the effect of deposition temperature

Journal Article · Fri Mar 21 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4868091· OSTI ID:22271321

Weerakkody, A. D.; Sedghi, N.; Hall, S. ^[1]; Althobaiti, M.; Dhanak, V. R.; Linhart, W. M.; Veal, T. D. ^[2]; Chalker, P. R. ^[3]; Tsoutsou, D.; Dimoulas, A. ^[4]

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1. Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ (United Kingdom)
2. Department of Physics and Stephenson Institute for Renewable Energy, University of Liverpool, Liverpool L69 7ZF (United Kingdom)
3. Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom)
4. NCSR Demokritos, MBE Laboratory, Institute of Materials Science, 153 10 Athens (Greece)

A study into the optimal deposition temperature for ultra-thin La{sub 2}O{sub 3}/Ge and Y{sub 2}O{sub 3}/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 (La{sub 2}O{sub 3} and Y{sub 2}O{sub 3}) 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. La{sub 2}O{sub 3} has been found to be more reactive to Ge than Y{sub 2}O{sub 3}, forming LaGeO{sub x} and a Ge sub-oxide at the interface for all deposition temperature studied, in the range from 44 °C to 400 °C. In contrast, Y{sub 2}O{sub 3}/Ge deposited at 400 °C allows for an ultra-thin GeO{sub 2} layer at the interface, which can be eliminated during annealing at temperatures higher than 525 °C leaving a pristine YGeO{sub x}/Ge interface. The Y{sub 2}O{sub 3}/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 Y{sub 2}O{sub 3}/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 Y{sub 2}O{sub 3}/Ge stack exhibits a higher conduction band offset (>2.3 eV) than the La{sub 2}O{sub 3}/Ge (∼2 eV), has a larger band gap (by about 0.3 eV), a germanium sub-oxide free interface, and leakage current (∼10{sup −7} A/cm{sup 2} at 1 V) five orders of magnitude lower than the respective La{sub 2}O{sub 3}/Ge stack. Our study strongly points to the superiority of the Y{sub 2}O{sub 3}/Ge system for germanium interface engineering to achieve high performance Ge Complementary Metal Oxide Semiconductor technology.

• OSTI ID: 22271321
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
ELLIPSOMETRY
FAR ULTRAVIOLET RADIATION
GERMANIUM OXIDES
INTERFACES
LANTHANUM OXIDES
LAYERS
LEAKAGE CURRENT
TEMPERATURE DEPENDENCE
THIN FILMS
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY
YTTRIUM OXIDES