Double barrier heights in 5,6,11,12-tetraphenylnaphthacene (rubrene) based organic Schottky diode

5,6,11,12-Tetraphenylnaphthacene (rubrene) was grown on p type Si (100) substrate using spin coating technique. We have fabricated an Al/rubrene/p-Si Schottky device and measured the current-voltage (I-V) characteristics in the temperature range from 75 to 300 K by steps of 25 K. An abnormal decrease in the experimental barrier height ΦB and an increase in the ideality factor n with a decrease in temperature have been observed. The I-V characteristics of Al/rubrene/p-Si Schottky diode are analyzed on the basis of thermionic emission (TE) theory and the assumption of double Gaussian distribution of barrier heights due to barrier inhomogeneities. The modified Richardson plots of ln(I0/T2)-(1/2)( qσ s0(i)/kT)2 versus 1000/T gives Φ̄B0(i) and AR(i) values as 1.186 and 0.571 eV, and 33.85 and 84.63 A cm-2 K-2, respectively. The modified Richardson constant value of AR (2)=33.85 A cm-2 K-2 for high temperature range (175-300 K) is very close to the theoretical value of 32 A cm-2 K-2 for p-Si. © 2013 Elsevier B.V. All rights reserved.