Temperature dependent electronic transport properties of heterojunctions formed between perovskite SrTiO3 nanocubes and silicon

Abstract

In this study, synthesized strontium titanate (SrTiO3) nanocubes were coated on n-Si semiconductor by spin coating to obtain a heterojunction device. Transmission electron microscopy image, scanning electron microscope image and x-ray diffraction patterns of thin film of SrTiO3 nanocubes coated on Si surface were taken for structural and morphological characterization of the material. The basic device parameters such as ideality factor (n) and barrier height (Φb) values of the reference Ni/Si/Al metal–semiconductor diode and of the Ni/SrTiO3/n-Si/Al heterojunction devices were calculated with the thermionic emission (TE) theory. The n and Φb values of the reference Ni/n-Si/Al device were calculated as 1.93 and 0.60 eV, respectively at room temperature. On the other hand, lower n and higher Φb values of Ni/SrTiO3/n-Si/Al heterojunction device were calculated as 1.34 and 0.63 eV, respectively. With these results, the current–voltage (I–V) measurements of the heterojunction device in the 80–400 K range were taken and the n, Φb, series resistance (Rs) values were calculated depending on the temperature by using different methods such as TE, Cheung and Norde functions. It was observed that while the temperature values decreased, n and Rs values of the device increase and Φb value decreases. The results obtained showed that the charge transport system is compatible with TE. The device parameters calculated from the Cheung and Norde methods also showed similar changes depending on the temperature. However, since the calculation method is different according to the TE method, different values were obtained in the device parameters. In addition, the curve Φb and (1/n)−1 against (1/2kT) was observed in accordance with the double Gauss distribution of the barrier heights. It was seen that the reverse bias I–V characteristics of the Ni/SrTiO3/n-Si/Al can be used in thermal sensors applications.