On the electrical characteristics of the Al/rhodamine-101/p-Si MS structure at low temperatures

Abstract

In this paper, the current–voltage (I–V) characteristics of Al/Rhodamine-101/p-Si/Al metal–semiconductor (MS) structures have been measured at temperatures ranging from 80 to 325K. The nonpolymeric organic compound rhodamine-101 (Rh101) film on a p-type Si substrate has been formed by means of the evaporation process and the Sn/rhodamine-101/Si contacts have been fabricated. The current–voltage characteristics of the diode show rectifying behaviour consistent with a potential barrier formed at the interface. The obtained I–V barrier heights (Φb) were in the range of 0.287–0.820eV with ideality factors (n) of 6.31–2.68. The high values of ideality factor (n) may be ascribed to decrease of the exponentially increase rate in current due to space-charge injection into Rh101 thin film at higher voltage. The temperature-dependent I–V characteristics of the Al/Rhodamine-101/p-Si/Al structure have shown a Gaussian distribution giving mean barrier height of 0.918eV and standard deviation of 0.104V. The mean barrier height (Φ¯bo) and the Richardson constant (A⁎) values were obtained as 1.046eV and 31.87AK−2cm−2, respectively, by means of the modified Richardson plot, ln[(I0/T2)–(q2σ02/2k2T2)] plot 1/kT. The value of Richardson constant A⁎ obtained from this plot is approximately the same with theoretical value of 32Acm−2K−2 for p-Si. As a result, it can be concluded that the temperature dependent characteristic parameters for Al/Rhodamine-101/p-Si structure can be successfully explained on the basis of TE mechanism with Gaussian distribution of the barrier height