Specific Contact Resistivity Reduction Through Ar Plasma-Treated TiO<sub>2−x</sub> Interfacial Layer to Metal/Ge Contact

Kim, Gwang-Sik; Kim, Jeong‐Kyu; Kim, Seunghwan; Jo, Jaesung; Shin, Changhwan; Park, Jin‐Hong; Saraswat, Krishna C.; Yu, Hyun‐Yong

doi:10.1109/led.2014.2354679

Cited by 34 publications

(30 citation statements)

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“…The x in GeO x for 10 cycles Fig. 3 Comparison of specific contact resistivity for PEALD TiO 2 and thermal ALD TiO 2 , inserted sample and thermal ALD TiO 2 sample [10]. Inset is the corrected resistance versus distance for PEALD TiO 2 inserted samples sample is 3.319 and for 30 cycles sample is 3.682.…”

Section: Resultsmentioning

confidence: 99%

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Zhang

Liu

Han

et al. 2018

Micro & Nano Letters

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A simple method is used to improve metal/n-germanium (Ge) contact characteristics by inserting plasma-enhanced atomic layer deposition (PEALD) deposited titanium dioxide (TiO 2)/GeO x. Cross-sectional transmission electron microscope results confirm the thickness of the 30 PEALD cycles TiO 2 /GeO x is 1.62/1.38 nm. By inserting 1.62/1.38 nm TiO 2 /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 cm 2 for Al/IL/n-Ge with an n-Ge concentration of 6 × 10 16 cm −3 was achieved. ρ c reduced by a factor 83 compared with no TiO 2 IL, and it also shows 4.72 times reduction compared with ρ c extracted from samples inserting thermal ALD-deposited TiO 2. 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 TiO 2 was oxygen-vacancies rich, which may dope TiO 2 and may contribute to lower tunnelling resistance. All of the characteristics will be beneficial for low contact resistivity.

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Section: Resultsmentioning

confidence: 99%

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Zhang

Liu

Han

et al. 2018

Micro & Nano Letters

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“…The displacement of the effective Fermi level at a metal and a semiconductor (silicon or III–V materials) contact has been explained by the Fermi‐level pinning effect or metal‐induced gap states . Even though the shift of the effective Fermi level should undergo further theoretical study, it is possible to try an experimental counter measure that was developed to alleviate the Fermi‐level displacement, i.e., inserting an ultrathin interfacial dielectric layer between a metal and a TMD layer …”

Section: Contact Resistance and Field‐effect Mobility For Various Fetsmentioning

confidence: 99%

Complementary Unipolar WS₂ Field‐Effect Transistors Using Fermi‐Level Depinning Layers

Park

Kim

Jung

et al. 2015

Adv Elect Materials

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In this study, a 20 cycle atomic layer-deposited (ALD) TiO 2 dielectric interfacial layer was inserted between WS 2 and other metals (Ti and Pd) to lower the Schottky barrier height through a mechanism such as Fermi-level depinning as in a silicon device. In addition to dramatically reducing contact resistance, unipolar transfer characteristics could be achieved in WS 2 FETs by using a TiO 2 dielectric interfacial layer with both low and high work function metal-WS 2 contact systems (Ti-WS 2 and Pd-WS 2 , respectively).Figure 1 a shows the schematic of a back-gate WS 2 FET with a 20 cycle ALD TiO 2 interfacial layer. The channel length and width are ≈3 and ≈20 µm, respectively. A lattice constant of 0.65 nm for the WS 2 was confi rmed as shown in a representative high resolution transmission electron microscopy (HRTEM) image of the metal-TiO 2 -WS 2 stack (Figure 1 b). TiO 2 thickness ≈2.7 nm is expected based on the deposition rate of 0.135 nm per cycle. The fi gure inset is an electron diffraction pattern obtained from a Ti-TiO 2 -WS 2 stack structure. Raman spectra for bi-and multilayer WS 2 are shown in Figure 1 c, and corresponding optical images are shown in Figure 1 d. The Raman spectra for WS 2 include two modes: the E 1 2g mode, which corresponds to the in-plane vibrational motion of atoms, and the A 1g mode, which is attributed to the out-of-plane vibrational motion of atoms. The thickness of the WS 2 layer can be extracted from the shift in the wavenumber. As the thickness increases, the wavenumber between E 1 2g and A 1g and the absolute intensity increase, while the intensity ratio of E 1 2g to A 1g decreases. [ 43 ] Figure 2 a shows the transfer characteristics ( I DS -V BG ) of WS 2 FETs with a Ti electrode (work function ≈4.3 eV). The drain bias was increased from 0.1 to 0.5 V in 0.1 V steps. The transfer characteristics showed bipolar behavior with a hole current for the negative gate bias region and electron current for the positive gate bias region. This is typical behavior for Schottky barrier FETs with a midgap-like contact metal. The effective position of the Fermi level appears to have shifted to the near midgap of WS 2 , forming a high Schottky barrier for both electrons and holes as shown in Figure 2 e. With a metal-semiconductor contact, when the effective workfunction of a metal is shifted by extrinsic mechanisms, the barrier height can be defi ned considering the Fermi-level pinning factor as shown in the equation below 1 B,n 0 gs M s gs 0where B,n 0 Φ is the barrier height, M φ is the work function of the metal electrode, s χ is the electron affi nity of the semiconductor, gs γ is parameter for the gap states, and 0 φ is a charge neutrality position. [ 44 ] The shift in the location of Fermi level can be caused by many factors such as surface states, metal-induced gap states (MIGS), defect states, or disorder-induced gap states, etc. [36][37][38]45,46 ] Recently, 2D transition metal dichalcogenides (TMDs) have attracted intense research interests due to their unique electrical, optica...

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“…10 . For the heavily doped n + -Ge contact sample, Al/ZnO/n + -Ge contacts shown the smaller ρ c in comparison with those of Ni/GeSn [ 40 , 41 ], Ni/Ge [ 42 ], Ti/n + -Ge in ref. [ 31 ], and Ti/TiO 2 /GeO 2 /Ge [ 31 ], carbon implanted Ni/Ge [ 42 ], and Ti/n + -SiGe/n-Ge [ 43 ].…”

Section: Resultsmentioning

confidence: 99%

Reduced Contact Resistance Between Metal and n-Ge by Insertion of ZnO with Argon Plasma Treatment

Zhang

Han

et al. 2018

Nanoscale Res Lett

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We investigate the metal-insulator-semiconductor contacts on n-Ge utilizing a ZnO interfacial layer (IL) to overcome the Fermi-level pinning (FLP) effect at metal/Ge interface and reduce the barrier height for electrons. A small conduction band offset of 0.22 eV at the interface between ZnO and n-Ge is obtained, and the ZnO IL leads to the significant reduced contact resistance (Rc) in metal/ZnO/n-Ge compared to the control device without ZnO, due to the elimination of FLP. It is observed that the argon (Ar) plasma treatment of ZnO can further improve the Rc characteristics in Al/ZnO/n-Ge device, which is due to that Ar plasma treatment increases the concentration of oxygen vacancy Vo, acting as n-type dopants in ZnO. The ohmic contact is demonstrated in the Al/ZnO/n-Ge with a dopant concentration of 3 × 1016 cm−3 in Ge. On the heavily doped n+-Ge with a phosphor ion (P+) implantation, a specific contact resistivity of 2.86 × 10− 5 Ω cm2 is achieved in Al/ZnO/n+-Ge with Ar plasma treatment.

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Specific Contact Resistivity Reduction Through Ar Plasma-Treated TiO_2−x Interfacial Layer to Metal/Ge Contact

Cited by 34 publications

References 10 publications

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Complementary Unipolar WS₂ Field‐Effect Transistors Using Fermi‐Level Depinning Layers

Reduced Contact Resistance Between Metal and n-Ge by Insertion of ZnO with Argon Plasma Treatment

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Specific Contact Resistivity Reduction Through Ar Plasma-Treated TiO2−x Interfacial Layer to Metal/Ge Contact

Cited by 34 publications

References 10 publications

Improving metal/ n ‐Ge ohmic contact by inserting TiO 2 deposited by PEALD

Improving metal/ n ‐Ge ohmic contact by inserting TiO 2 deposited by PEALD

Complementary Unipolar WS2 Field‐Effect Transistors Using Fermi‐Level Depinning Layers

Reduced Contact Resistance Between Metal and n-Ge by Insertion of ZnO with Argon Plasma Treatment

Contact Info

Product

Resources

About

Specific Contact Resistivity Reduction Through Ar Plasma-Treated TiO_2−x Interfacial Layer to Metal/Ge Contact

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Improving metal/ n ‐Ge ohmic contact by inserting TiO ₂ deposited by PEALD

Complementary Unipolar WS₂ Field‐Effect Transistors Using Fermi‐Level Depinning Layers