Increase in Current Density at Metal/GeO2/n-Ge Structure by Using Laminated Electrode

Abstract

In a metal/n-Ge structure, Fermi level pinning tends to occur. The insertion of an oxide layer at the interface between electrodes and n-Ge can effectively reduce the Schottky barrier height. However, the attachment of metal and oxide can cause diffusion of oxygen to the metal due to Gibbs free energy, which degrades the contact characteristics. In this study, we investigated the effects of a laminated electrode on the current density at a metal/GeO2/n-Ge structure. Ni, Pt, Al, or Ti layers with thicknesses of 0.5–20 nm were formed, followed by a deposition of 200-nm-thick Al. The JV curves of these samples showed that the current density of the Al/Ti/GeO2/n-Ge structure was the largest among them and was about 126 times larger than that of the Al/GeO2/n-Ge structure. We also found that the current density depended on the film thickness of Ti and was the highest at the film thickness of about 2.5 nm or less. To investigate the effect of the Ti interlayer on the current density, we obtained the depth profiles of X-ray photoelectron spectroscope spectra of the Al/Ti/GeO2/n-Ge and Al/GeO2/n-Ge structures. Analysis showed that the diffusion of the oxygen to Al was limited by the 20-nm-thick Ti, and the oxygen was diffused to Al when the film thickness of Ti was about 1 nm. These results demonstrate that laminated oxide structures such as AlOx/TiOx and TiOx/GeO2 can form on the sample with 1-nm-thick Ti, which increases the current density.

Graphic Abstract

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4

References

  1. 1.

    Wirths, S., Geiger, R., von den Driesch, N., Mussler, G., Stoica, T., Mantl, S., Ikonic, Z., Luysberg, M., Chiussi, S., Hartmann, J.M., Sigg, H., Faist, J., Buca, D., Grützmacher, D.: Lasing in direct-bandgap GeSn alloy grown on Si. Nat. Photonics 9, 88–92 (2015)

    CAS  Article  Google Scholar 

  2. 2.

    Stange, D., von den Driesch, N., Rainko, D., Roesgaard, S., Povstugar, I., Hartmann, J.M., Stoica, T., Ikonic, Z., Mantl, S., Grützmacher, D., Buca, D.: Short-wave infrared LEDs from GeSn/SiGeSn multiple quantum wells. Optica 4, 185–188 (2017)

    CAS  Article  Google Scholar 

  3. 3.

    Dimoulas, A., Tsipas, P., Sotiropoulos, A., Evangelou, E.K.: Fermi-level pinning and charge neutrality level in germanium. Appl. Phys. Lett. 89, 252110 (2006)

    Article  Google Scholar 

  4. 4.

    Nishimura, T., Kita, K., Toriumi, A.: Evidence for strong Fermi-level pinning due to metal-induced gap states at metal/germanium interface. Appl. Phys. Lett. 91, 123123 (2007)

    Article  Google Scholar 

  5. 5.

    Nishimura, T., Kita, K., Toriumi, A.: A significant shift of Schottky barrier heights at strongly pinned metal/germanium interface by inserting an ultra-thin insulating film. Appl. Phys. Express 1, 051406 (2008)

    Article  Google Scholar 

  6. 6.

    Seo, Y., Lee, T.I., Ahn, H.J., Moon, J., Hwang, W.S., Yu, H.-Y., Cho, B.J.: Fermi level depinning in Ti/GeO2/n-Ge via the interfacial reaction between Ti and GeO2. IEEE Trans. Electron Devices 64, 4242–4245 (2017)

    CAS  Article  Google Scholar 

  7. 7.

    Lin, J.-Y.J., Roy, A.M., Nainani, A., Sun, Y., Saraswat, K.C.: Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height. Appl. Phys. Lett. 98, 092113 (2011)

    Article  Google Scholar 

  8. 8.

    Kim, G.-S., Kim, J.-K., Kim, S.-H., Jo, J., Shin, C., Park, J.-H., Saraswat, K.C., Yu, H.-Y.: Specific contact resistivity reduction through Ar plasma-treated TiO2−x interfacial layer to metal/Ge contact. IEEE Electron Device Lett. 35, 1076–1078 (2014)

    CAS  Article  Google Scholar 

  9. 9.

    Dev, S., Remesh, N., Rawal, Y., Manik, P.P., Wood, B., Lodha, S.: Low resistivity contact on n-type Ge using low work-function Yb with a thin TiO2 interfacial layer. Appl. Phys. Lett. 108, 103507 (2016)

    Article  Google Scholar 

  10. 10.

    Qin, X., Shu, G., Qu, X.-P.: Role of post-deposition annealing of sputtered Ti on Fermi level depinning in Ti/TiOx/n-Ge. ECS J. Solid State Sci. Technol. 8, P153–P158 (2019)

    CAS  Article  Google Scholar 

  11. 11.

    Zhou, Y., Ogawa, M., Han, X., Wang, K.L.: Alleviation of Fermi-level pinning effect on metal/germanium interface by insertion of an ultrathin aluminum oxide. Appl. Phys. Lett. 93, 202105 (2008)

    Article  Google Scholar 

  12. 12.

    Manik, P.P., Mishra, R.K., Kishore, V.P., Ray, P., Nainani, A., Huang, Y.-C., Abraham, M.C., Ganguly, U., Lodha, S.: Fermi-level unpinning and low resistivity in contacts to n-type Ge with a thin ZnO interfacial layer. Appl. Phys. Lett. 101, 182105 (2012)

    Article  Google Scholar 

  13. 13.

    Zhang, Y., Han, G., Wu, H., Wang, X., Liu, Y., Zhang, J., Liu, H., Zheng, H., Chen, X., Liu, C., Hao, Y.: Reduced contact resistance between metal and n-Ge by insertion of ZnO with argon plasma treatment. Nanoscale Res. Lett. 13, 237 (2018)

    Article  Google Scholar 

  14. 14.

    Yamamoto, K., Mitsuhara, M., Hiidome, K., Noguchi, R., Nishida, M., Wang, D., Nakashima, H.: Role of an interlayer at a TiN/Ge contact to alleviate the intrinsic Fermi-level pinning position toward the conduction band edge. Appl. Phys. Lett. 104, 132109 (2014)

    Article  Google Scholar 

  15. 15.

    Biswas, D., Biswas, J., Ghosh, S., Wood, B., Lodha, S.: Enhanced thermal stability of Ti/TiO2/n-Ge contacts through plasma nitridation of TiO2 interfacial layer. Appl. Phys. Lett. 110, 052104 (2017)

    Article  Google Scholar 

  16. 16.

    Roy, A.M., Lin, J.Y.J., Saraswat, K.C.: Specific contact resistivity of tunnel barrier contacts used for Fermi level depinning. IEEE Electron Device Lett. 31, 1077–1079 (2010)

    CAS  Article  Google Scholar 

  17. 17.

    Ohta, A., Fujioka, T., Murakami, H., Higashi, S., Miyazaki, S.: X-ray photoelectron spectroscopy study of interfacial reactions between metal and ultrathin Ge oxide. Jpn. J. Appl. Phys. 50, 10PE01 (2011)

    Article  Google Scholar 

  18. 18.

    Ogawa, S., Hideshima, I., Minoura, Y., Yamamoto, T., Yasui, A., Miyata, H., Kimura, K., Ito, T., Hosoi, T., Shimura, T., Watanabe, H.: Interface engineering between metal electrode and GeO2 dielectric for future Ge-based metal-oxide-semiconductor technologies. Appl. Phys. Lett. 101, 201601 (2012)

    Article  Google Scholar 

  19. 19.

    Kim, G.-S., Kim, S.-W., Kim, S.-H., Park, J., Seo, Y., Cho, B.J., Shin, C., Shim, J.H., Yu, H.-Y.: Effective Schottky barrier height lowering of metal/n-Ge with a TiO2/GeO2 interlayer stack. ACS Appl. Mater. Interfaces. 8, 35419–35425 (2016)

    CAS  Article  Google Scholar 

Download references

Acknowledgements

This research and development was supported by MIC/SCOPE #165103005. The work was partly carried out in the Advanced ICT Devices Lab at NICT.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Takahiro Tsukamoto.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Tsukamoto, T., Kurihara, S., Hirose, N. et al. Increase in Current Density at Metal/GeO2/n-Ge Structure by Using Laminated Electrode. Electron. Mater. Lett. 16, 41–46 (2020). https://doi.org/10.1007/s13391-019-00185-0

Download citation

Keywords

  • Pinning
  • n-Ge
  • Laminated electrode
  • Ti
  • GeO2