Electrical Properties of Pt/n-Ge Schottky Contact Modified Using Copper Phthalocyanine (CuPc) Interlayer

Abstract

We investigated the electrical properties and reverse leakage mechanisms of Pt/n-Ge Schottky contacts with copper phthalocyanine (CuPc) as an interlayer. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky contacts were used to evaluate Schottky barrier parameters such as ideality factor, barrier height, and series resistance. The barrier heights and ideality factors measured from the forward bias I-V characteristics were found to be 0.50 eV and 1.06 for Pt/n-Ge Schottky contact, and 0.58 eV and 1.31 for Pt/CuPc/n-Ge Schottky contact, respectively. Cheung method was used to measure the series resistances of the Schottky contacts, and the consistency was checked using the Norde method. The reverse leakage conduction mechanism of the Schottky contacts was investigated. Pt/CuPc/n-Ge Schottky contacts showed a transition from Schottky emission to Poole-Frenkel emission at a higher bias range. This could be associated with the high density of structural defects or traps associated with the organic material. Germanium (Ge) is a promising channel material for nextgeneration high mobility complementary metal-oxide-semiconductor (CMOS) devices in terms of overcoming the scaling limits of its Si counterpart. 1 Recently, there has been renewed interest in metalGe Schottky contacts for the following reasons: (1) Ge has double the electron mobility and four times the hole mobility in low electric fields compared to Si, thus making high speed complementary field effect transistors (FETs) a possibility; 2 (2) Ge plays a main role in very large scale integrated (VLSI) technology due to its compatibility with main stream Si; 3 and (3) metal-semiconductor (MS) contacts play an important role in the performance of semiconductor devices due to their potential application in various electronic and optoelectronic devices such as microwave diodes, Schottky barrier metal-oxide-semiconductor field-effect transistors (SB-MOSFETs), solar cells, chemical sensors, and photo detectors. 4-6 Due to the technological importance of the Schottky barrier diodes (SBDs), a full understanding of the nature of their electrical characteristics is of great interest. Many SBDs are not intimate MS contacts; rather, they have a metal-interfacial layer-semiconductor structure unless specially fabricated. It is well known that the electrical characteristics of SBDs are controlled mainly by its interfacial layer. The interfacial layer formed at the interface between metal and semiconductor substrate has a rectification behavior in which the values of barrier height and ideality factor are greater than in conventional metal/semiconductor structures. This behavior has been attributed to the space charge region of the semiconductor, which is influenced by the interfacial layer in metal/semiconductor structures.Until now, many researchers have investigated the formation of metal/Ge Schottky systems. Dimoulas et al. 7 and Nishimura et al. 8 investigated current-voltage (I-V) characteristics of various metal/Ge junctions. They rep...

Energy-level alignment and electrical properties of Al/p-type Si Schottky diodes with sorbitol-doped PEDOT:PSS as an organic interlayer

“…The growth of organic thin films on inorganic semiconductor substrates can modify the electronic properties of the metal/semiconductor MS contacts, since the Schottky barrier heights of metal-semiconductor contacts are changed by the formation of a dipole layer between the semiconductor and the organic film [8]. For instance, the insertion of a copper phthalocyanine (CuPc) interlayer in between a Pt film and a Ge substrate changes the Schottky barrier height of this interface [9].…”

Modification of Schottky Barrier Properties of Ti/p-type InP Schottky Diode by Polyaniline (PANI) Organic Interlayer

“…However, unlike Ti/p-type InP Schottky diode without PANI interlayer, the slope in region-IV of Ti/ptype InP Schottky diode with PANI interlayer was much higher than 2 in spite of high injection level, implying that space-charge-limited current still predominated even at higher voltages. This is due to numerous traps originated from structural defects prevailing in organic PANI interlayer caused by its non-uniformity and sub atomic structure [41,42].…”

Effect of Rapid Thermal Annealing on the Electrical and Structural Properties of Se Schottky Contacts to n-Type Si

“…Therefore, there is a discrepancy between barrier heights calculated from Norde's and forward IV methods. The series resistance of Se/n-type Si Schottky diode was evaluated from the forward bias IV data using the method developed by Cheung. 19) The forward bias IV characteristics due to thermionic emission of the Schottky contact with the series resistance can be expressed using Cheung's function, as given by 19,20) …”