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

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 325 K. 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 0.287-0.820 eV 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 0.918 eV and standard deviation of 0.104 V. The mean barrier height (Φ¯bo) and the Richardson constant (A⁎) values were obtained as 1.046 eV and 31.87 A K−2 cm−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 32 A cm−2 K−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