Richardson constant and characteristics of pentacene organic planar Schottky diode

Abstract

Planar organic Schottky diodes were fabricated using undoped pentacene as an active layer with both palladium and aluminum as contacts. Pentacene organic thin films were deposited on n-type silicon substrates with 100 (n-Si<100>) and 111 (n-Si<111>) orientations. X-ray diffraction (XRD) measurements revealed that the pentacene films’ XRD patterns exhibit several peaks with various orientations. The energy-dispersive X-ray technique was used for chemical analysis of the pentacene, and scanning electron microscopy was used to characterize the surface morphology. A structural and morphological study of the deposited pentacene indicates a polycrystalline triclinic (anorthic) nature. A current–voltage curve was experimentally constructed at temperatures (T) ranging from 300 K to 360 K with a step of 15 K. The diode parameters, such as saturation current, ideality factor (n), and barrier height (ΦB), were systematically analyzed using thermionic emission theory. The fabricated devices exhibit decreasing n and increasing ΦB values with increasing T. Richardson's constant for pentacene was calculated, which indicated that the conventionally calculated value from the temperature-dependent characteristic curve is much lower than the calculated theoretical value. It was also observed that the device deposited over the n-Si<111> substrate exhibited larger forward and lower reverse currents than the n-Si<100> substrate device.