Journal of Alloys and Compounds 481 (2009) 427–433 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Study of Gaussian distribution of inhomogeneous barrier height for n-InSb/p-GaAs heterojunction prepared by flash evaporation A.A.M. Farag a,∗ , F.S. Terra b , G.M. Mahmoud b , A.M. Mansour b a Thin Film Laboratory, Physics Department, Faculty of Education, Ain Shams University, Cairo 11757, Roxy, Heliopolis, Egypt b Physics Department, National Research Center, Dokki, Cairo, Egypt article info Article history: Received 3 January 2009 Received in revised form 26 February 2009 Accepted 2 March 2009 Available online 14 March 2009 Keywords: Gaussian distribution Barrier height n-InSb/p-GaAs Flash evaporation abstract n-Type indium antimonide (n-InSb) films were successfully fabricated on p-GaAs monocrystalline sub- strates by flash evaporation technique. The elemental composition of the prepared films was confirmed by energy dispersive X-ray (EDX) spectroscopy. The morphology and crystal structure of the film were char- acterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The Gaussian distribution model was used to analyze the anomalies observed in current–voltage characteristics of n- InSb/p-GaAs heterojunctions. The barrier height obtained from C–V measurement is higher than obtained from I–V measurement and this discrepancy can be explained by introducing a spatial distribution of barrier heights due to barrier height inhomogeneities. © 2009 Elsevier B.V. All rights reserved. 1. Introduction InSb-based heterostructures are highly promising materials for mid-infrared optoelectronic devices, due to the narrowest possible band gap and smallest carrier effective mass among III–V com- pounds [1]. For application in electronic devices, InSb thin layers must be grown on semi-insulating substrates to prevent current leakage, but no suitable lattice-matched semi-insulating substrate exists for InSb [2]. The growth of high-quality InSb films by the layer by layer growth process is difficult because a large lattice mismatch between GaAs and InSb creates misfit strains and immis- cibility problems [3]. The heteroepitaxy of InSb films on GaAs or Si substrate has been reported by many groups using a wide vari- ety of preparation methods such as molecular beam epitaxy (MBE) [4–7], metal-organic chemical vapor deposition (MOCVD) [8–11] and magnetron sputtering (MS) [12,13]. However, to the best of our knowledge there is no report on the growth of such heterostruc- ture by flash evaporation, FE technique. Here we report the growth of InSb/GaAs heterostructure employing FE technique wherein we have overcome many of the problems associated with the growth by optimizing several parameters, such as III/V mass ratio and growth temperature. As a result, we have grown InSb layers which exhibit structural coherence and reasonably good electrical prop- erties. In this paper, in order to achieve a better understand of the interface in the n-InSb/p-GaAs heterojunction prepared by flash ∗ Corresponding author. E-mail address: alaafaragg@yahoo.com (A.A.M. Farag). evaporation technique under high vacuum, the current–voltage and capacitance–voltage characteristics in dark at different tempera- tures were measured. Also, the aim of this research was to establish a relationship between the parameters deduced from the I–V and C–V characteristics. 2. Experimental procedure 2.1. Fabrication of n-InSb/p-GaAs heterojunction p-Type GaAs wafer with (1 0 0) orientation and  = 5–10  cm resistivity was used as substrate in this study. The substrate was chemically cleaned using the RCA cleaning procedure (i.e. boiling in NH4 +H2O2 +6·H2O for 10 min followed by a 10 min boil in HCl + H2O2 +6·H2O). InSb thin films were prepared on GaAs by flash evaporation technique under 10 -4 Pa onto pre-cleaned GaAs substrates held at a temperature ∼ 340 K using a high vacuum coating unit (Edwards E 306 A, England). The flash evaporation attach- ment was nearly similar to that described in [14]. The thickness of InSb films was monitored with the help of a digital quartz thickness monitor as ∼ =1.4 m. 2.2. Characterization techniques The structural properties of the films were investigated by X-ray diffraction (XRD), Glancing incidence X-ray diffraction was performed to study the crystallinity of the films using analytical X’Pert PRO MRD diffractometer with Cu K radiation at 0.5 ◦ incidence angle. The film morphology was investigated by scanning electron microscopy (SEM) using Model Philips XL 30 attached with EDX Unit, with accel- erating voltage 30 kV, magnification 10× up to 400,000× and 3.5 nm resolution for EDX. Gold electrode was first evaporated on InSb through suitable mask to form a front ohmic electrode and other gold layer was evaporated on GaAs as back electrode, so as to form Au/InSb/GaAs/Au heterojunction. In order to measure the electrical properties of the heterojunction, electrical contacts were equipped with copper wires mechanically applied to the two metal electrodes using thermosetting 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.03.004