Journal of Alloys and Compounds 492 (2010) 649–655 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Thermal annealing behaviour of platinum, nickel and titanium Schottky barrier diodes on n-Ge (1 0 0) A. Chawanda a,b,∗ , C. Nyamhere a , F.D. Auret a , W. Mtangi a , M. Diale a , J.M. Nel a a Department of Physics, University of Pretoria, Pretoria 0002, South Africa b Department of Physics, Midlands State University, Bag 9055, Gweru, Zimbabwe article info Article history: Received 26 August 2009 Received in revised form 25 November 2009 Accepted 28 November 2009 Available online 5 December 2009 Keywords: Schottky contact Germanium Annealing Ideality factor Agglomeration abstract Platinum (Pt) and titanium (Ti) Schottky barrier diodes were fabricated on bulk grown (1 0 0) Sb-doped n- type germanium using the electron beam whereas nickel (Ni) contacts were fabricated using the resistive evaporation system. Electrical characterization of these contacts using current–voltage (I–V) measure- ments was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transfor- mation during the annealing process. The results have also revealed that Pt Schottky contacts are of a high quality, with low reverse currents in the order of (10 -5 to 10 -6 ) A and as-deposited ideality factors as low as 1.09. Furthermore, the samples microstructural characterization was performed by scanning electron microscopy (SEM) at different annealing temperatures. From the results, it can be concluded that the onset temperature in 30 nm Ni- and Pt/n-Ge (1 0 0) systems occurs at 500–600 ◦ C and 600–700 ◦ C, respectively. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The solid phase reaction at sub-eutectic temperatures between a thin metal film and a single-crystal semiconductor has attracted much interest because of its importance in Schottky barrier and contact formation, epitaxial growth and device reliability [1].A good metal-semiconductor (MS) contact is essential for the suc- cessful operation of the electronic circuits and devices [2]. Contacts to very large scale integration (VLSI) circuits and interconnec- tions require MS contacts which are thermally stable, have low resistivity and are compatible with the process technology. Due to the shrinking of the advanced Si-based complementary metal- oxide-semiconductor (CMOS) device feature size, new material and device structures to relax the physical limitation in device scal- ing are now required. Ge has been regarded as the replacement for Si as a channel material in future high-speed CMOS technol- ogy, because it offers two times higher intrinsic electron mobility and four times higher intrinsic hole mobility than that of Si [3]. As the possibility of using Ge in microelectronics arises, optimal implementation of germanium technology will require an under- standing of metal–germanium interactions from both metallurgical and electrical standpoints. ∗ Corresponding author at: Department of Physics, University of Pretoria, Pretoria 0002, South Africa. Tel.: +27 12 420 3508; fax: +27 12 362 5288. E-mail address: albert.chawanda@up.ac.za (A. Chawanda). The reactions of germanium with Pt have been studied [1,4–8], while with Ni have been reported by [4,5,9–15] and with Ti have been investigated [5,16]. The study of the solid state reac- tion between thin metal films and germanium to determine the phase formation sequence [1,4–6,10–13,15], microstructure of the material [4,5,7,16], growth kinetics [10,15] and electrical charac- teristics were analyzed by x-ray diffraction [1,4–6,10–13,15,16], Rutherford Backscattering spectroscopy [1], transmission electron microscopy [4,7,10], differential scanning calorimetry [7,10] and current–voltage (I–V) [4,6,11,12,14,16], techniques. Yao et al. [4] studied the I–V characteristics of Pt/n-Ge (0 0 1) and Ni/n-Ge (0 0 1) after subjecting the Schottky contacts to rapid thermal anneal (RTA) in N 2 ambient at 250–700 ◦ C for 20 s. Gumeniuk et al. [6] have reported the superconductivity in Pt germanides of new skutterditelike compounds MPt 4 Ge 12 . Laszcz et al. [7] studied the mechanisms of the Pt germanide formation by RTA processes in the Ge/Pt/Ge/SiO 2 structure at 200–600 ◦ C range. Their results depict that, during annealing of the Ge/Pt/Ge/SiO 2 structure at 200 ◦ C the whole Pt layer had reacted with a part of the Ge layer and after 300 ◦ C anneal the whole Ge reacted with Pt. Ohtsu et al. [8] investi- gated the reactions of the samarium platinum germanides ternary system using high-pressure techniques and a simple arc-melting method. Thanailakis et al. [9] established a relationship between as- deposited Ni/n-Ge (1 1 1) Schottky barrier height value, the metal work function and the density of surface states of the germanium substrate. Peng et al. [11] reported the Ni/n-Ge (1 0 0) Schottky diodes I–V characteristics and the nickel germanide induced strain 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.11.202