Physico-Chemical nanomaterials science

Influence of titanium nitride thin films on the electrical properties of isotype n-TiN/n-Si heterostructures
Ilashchuk M.I., Orletskyi I.G., Koziarskyi I.P., Koziarskyi D.P., Solovan M.N., Maistruk E.V., Parfenyuk O.A.
Yuriy Fedkovych Chernivtsi National University, 2 Kotsubynsky st., 58002 Chernivtsi, Ukraine.
E-mail: i.koziarskyi@chnu.edu.ua

Due to the successful combination of physico-chemical properties, thin titanium nitride films are widely used in various semiconductor devices. In particular, a wide band gap (Eg = 3.4 eV), a high transmittance in the visible and near infrared regions of the spectrum (T = 70 – 80 %), as well as a significant concentration of electrons (n = 1018 – 1019 cm–3) [1] make it possible to use TiN for photovoltaic conversion of solar energy.
The deposition of TiN thin films was performed on polished substrates of polycrystalline Si (electron concentration n = 3 × 1015 cm–3) by the method of reactive magnetron sputtering. The substrate temperature was 573 K. The thickness of the studied films d ~ 100 nm. The electron concentration calculated from electrical measurements was n ≈ 5 × 1018 cm−3.
Studies of I-V–characteristics of isotype n-TiN/n-Si heterostructures at forward and reverse biases in the temperature range T = 299 – 342 K indicate the rectifying properties of the structures. The rectification ratio at |V| = 1.5 V and T = 294 K was ~ 103. Based on the C-V–characteristics, the presence of potential barriers was established both in the TiN thin film (qk = 0.8 eV) and in the base material of the structure Si (qk = 0.23 eV). The concentrations of electrically active impurities in the quasi-neutral regions of the structure components and their thickness were determined: ND(TiN) ≈ 4 × 1018 cm–3 and ND(Si) = 2.8 × 1015 cm–3 and w(TiN) ≈ 15 nm and w(Si) = 340 nm, respectively. Analysis of the I-V–characteristics showed that the main mechanism of current transfer in the obtained n-TiN/n-Si heterojunctions, both at forward and reverse biases, is tunneling through a thin potential barrier in a high-conductivity TiN film.
A model of the energy diagram of the heterostructure is proposed. This model describes well the experimental electrophysical phenomena.

1.	Karlsson B., Shimshock R.P., Seraphin B.O. Haygarth J.C. Optical Properties of CVD-Coated TiN, ZrN and HfN // Physica Scripta.-1982.-25.-P. 775-779.