Improving metal/n-Ge ohmic contact by inserting TiO2 deposited by PEALD

Yi Zhang; Yan Liu; Genquan Han; Huan Liu; Yue Hao

Improving metal/n-Ge ohmic contact by inserting TiO₂ deposited by PEALD

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Author(s): Yi Zhang¹ ; Yan Liu¹ ; Genquan Han¹ ; Huan Liu¹ ; Yue Hao¹
- Affiliations: 1: Wide Bandgap Semiconductor Technology Disciplines State Key Laboratory , School of Microelectronics , Xidian University , Xi'an 710071 , People's Republic of China
Source: Volume 13, Issue 6, June 2018, p. 801 – 803
DOI: 10.1049/mnl.2017.0776 , Online ISSN 1750-0443

Received 06/11/2017, Accepted 09/02/2018, Revised 30/01/2018, Published 01/06/2018

A simple method is used to improve metal/n-germanium (Ge) contact characteristics by inserting plasma-enhanced atomic layer deposition (PEALD) deposited titanium dioxide (TiO₂)/GeO _x . Cross-sectional transmission electron microscope results confirm the thickness of the 30 PEALD cycles TiO₂/GeO _x is 1.62/1.38 nm. By inserting 1.62/1.38 nm TiO₂/GeO _x between aluminium (Al) and n-Ge, current densities increased by about 1800 times at −0.1 V compared with contacts without insertion layer (IL). With IL, ρ _c of 9.52 × 10⁻³ Ω cm² for Al/IL/n-Ge with an n-Ge concentration of 6 × 10¹⁶ cm⁻³ was achieved. ρ _c reduced by a factor 83 compared with no TiO₂ IL, and it also shows 4.72 times reduction compared with ρ _c extracted from samples inserting thermal ALD-deposited TiO₂. X-ray photoelectron spectroscopy (XPS) results shows that the valence state for GeO _x was 3.682, thus Ge surface may be passivated. It was also determined by XPS that TiO₂ was oxygen-vacancies rich, which may dope TiO₂ and may contribute to lower tunnelling resistance. All of the characteristics will be beneficial for low contact resistivity.

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Improving metal/n-Ge ohmic contact by inserting TiO₂ deposited by PEALD

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