In this contribution, we will report a fundamental study of the factors that set the contact resistivity between metals and highly doped semiconductors. We will investigate the case of n-type doped Si contacted with amorphous TiSi combining first-principles calculations with Non-Equilibrium Green functions transport simulations . We will show that, whereas the metal/semiconductor intrinsic contact resistivity initially scales with the doping concentration, it is found to saturate at ~2x10-10 Wcm2, as of a doping concentration of ~5x1021 cm-3. From this concentration on, electron injection is governed by Ohm’s law. It turns out that, in such high doping regimes, the electron injection does no longer depend on the barrier height set by the interface potential to be crossed. In turn, it becomes less sensitive to the chemical composition of the interface/degree of disorder and is limited by the intrinsic transmission probability of electrons being injected from the metal into the semiconductor. The latter depends on both the effective masses of the metal and of the semiconductor  and imposes an intrinsic physical limit to the contact resistance. We will show that, in this regime, contacting metals with a heavy electron effective mass are favorable to increase the transmission probability and, hence, to reduce of the semiconductor-metal intrinsic contact resistivity.
The authors thank the imec industrial affiliation core CMOS program and quantumwise for financial and technical supports, respectively.
- Hao Yu, Marc Schaekers, Jian Zhang, Lin-Lin Wang, Jean-Luc Everaert, Naoto Horiguchi, Yu-Long Jiang, Dan Mocuta, Nadine Collaert and Kristin De Meyer, IEEE TRANSACTIONS ON ELECTRON DEVICES, vol. 64, no. 2, pp.500 (2017).
- Hiroaki Niimi, Zuoguang Liu, Oleg Gluschenkov, Shogo Mochizuki, Jody Fronheiser, Juntao Li, James Demarest, Chen Zhang, Bei Liu, Jie Yang, Mark Raymond, Bala Haran, Huiming Bu, and Tenko Yamashita, IEEE ELECTRON DEVICE LETTERS, vol. 37, no. 11, pp. 1371 (2016).
- Ashish Baraskar, A. C. Gossard, and Mark J. W. Rodwell, Journal of Applied Physics, Vol. 114, pp. 154516 (2013).
- Atomistix ToolKit version 2016.1, QuantumWise A/S (www.quantumwise.com).
- M. Brandbyge, J.-L. Mozos, P. Ordejón, J. Taylor, and K. Stokbro, Phys. Rev. B 65, pp. 165401 (2002).