@1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 Comparison I-V Characteristics of Sb/c-Si and Al/c-Si Junction Fatin G. Hachim Department of Physics / College of Science / University of Thi -Qar Ramiz A. Al-Ansari Department of Physics / College of Science for Women / University of Baghdad Hussein Kh. AL-Lamy Department of Physics / College of Science/ University of Baghdad Received in: 15March 2012 , Accepted in: 21 May 2012 Abstract Hetero junctions are fabricated by depositing antimony (Sb) and Al films on n-type single crystal(c-Si) wafers by the method of vacuum evaporation with thickness (0.25µm), with rate of deposition equals to 2.77 Å/sec, all samples are annealed in a vacuum for one hour at 473K. The tests have shown that all the films have polycrystalline structure for all Sb films. The barrier heights in (Sb/c-Si) junction was found to be equal 0.825eV, but(Al/c-Si) junction ohmic contact. Current-voltage measurements confirm this behaviour. Keywords : Sb/Si heterojunctions, I-V characteristics of Sb/Si, structure properties of Sb. 153 | Physics @1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 Introduction Sb/Si junctions have attracted many attentions because their importance properties for this junction . It can be used as rectifying devices in electronic applications [1,2]. This junction is unipolar charge of minority carrier that’s dominat on contact operation which has only one kind of charges, by it we could get the rectifier character as a result of potential barrier that creates by finding stable space charges in semiconductor[3]. Antimony can be creates potential barrier with Si because resistivity and work function, but Al metal resistivity is low due to conduction in the metal. The Al metal was chosen as an ohmic contact with the c-Si layer [1]. The aim of this study is prepared Sb/c-Si and Al/c-Si Junction in order to study the Φb, Is and β as a function to annealing and thickness. Experimental part Sb and Al films were deposited on the silicon substrates by the method of vacuum evaporation (Type Edward coating system) with pressur 10-5 mbar. The thickness of each deposited thin film is (0.25µm), the junctions are annealed in a vacuum at a temperature of 437K for one hour. Sb structure was studied by X-ray diffraction Fig (1) comparative with standard value in ASTM, used a Philips x-ray diffractometer system which records the intensity as a function of Bragg's angle. The source of radiation was cu(kα) with wavelength λ=1.5406A°, the current was 30mA and the voltage was 40 kv, The current-voltage measurements in the dark were done for the Sb/Si heterojuntion by using keithley digital electrometer 616 and D.C. power supply. The bias voltage was varied in the range of (0 – 1.4) volt in the case of forward and reverse bias. From plots of the relation between the forward current and bias voltage, potential barrier height (Φb) can be determined from [4]: Is = A* T2 exp (-qΦb/KBT)…………………………….(1) where A* is the effective Richardson constant modified to take account of both the effective mass of the electrons in the semiconductor, kB is the Botzman's constant(1.3806×10-23 J/k), q is the electronic charge, T is the absolute temperature, the constant IS is the saturation current. Φb= 𝐾𝐵𝑇 𝑞 𝐿𝑛 𝐴 ∗𝑇2 𝐼𝑠 ………………………………………….(2) The ideality factor (β) can be determined by the relation :      ⋅=β S FB I ILn V TK q …………………………………….(3) Where If is the forward bias current , the ideality factor (β) is related to the various physical properties of the of heterojunction. Results and Discussion For Sb films prepared at R.T and Ta=473K with (0.25µm),from Fig (1) showed Sb films as a polycrystalline structure, but peaks intensity in fig(b1)increase with the increase of annealing a temperature caused by elimination of voids and the reduction of dangling bond concentration ( structural defects). These results are in agreement with [5]. These XRD peaks were shown to be the (003), (110) and (006) are listed in Table(1) according to ASTM system. The current voltage (I-V) characteristics of Al/Si all fabricated junctions of the forward- and reverse biased are shown in figure (2).It can be seen from this curve that the linear 154 | Physics @1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 relation shape behavior between current and voltage for all samples prepared with thickness (0.25µm) and annealed temperature of 473K. This behavior may be interpreted by the work function of Al and c-Si are nearly similar( that’s mean the junctions do not creat the depletion layer), (Φb) is zero or negative and electron can flow freely in the two directions .In ohmic contact no potential barrier will be formed between Al electrode and c-Si layer. These results are in agreement with [6]. But(I-V) characteristics of Sb/Si in Figure (3) show this curve the forward characteristics shows exponential behaviour, the current increasing rapidly with voltage according to equation (1), for all samples prepared with thickness (0.25µm) and annealed temperature of 473K , that’s mean the junctions creat the depletion layer(w) and barrier height(Φb). This is in good agreement with [7,8]. From this figure the current increases slightly with the increase of the annealing temperature because increasing temperatures cause a rearrangement of the interface atoms and reduce surface states and dislocalized at interface layer between a-Sb and c-Si which leads to the improvement of the junctions characteristics. This was in agreement with [9,1]. Also we can notice form Table (2) that the value of the ideality factor and saturation current decreases but potential barrier height increases with the increase of annealing temperature. This behavior attributed to reduction of dangling bonds as well as the density of states in Sb. Conclusions The structural nature of the Sb is Polycrystalline but after the annealing process crystallization of Sb films increases because of the decrease of the dangling bond. The current-voltage measurements of Sb/c-Si heterojunction case the value of ideality factor decreases with the increase of annealing temperatures but potential barrier height increases with the increase of annealing temperature, this behavior is attributed to reduction of dangling bonds as well as the density of states(defects) in Sb. References 1-Gong ,S.; Robertsson .H.Hentzell , Hultman .L.; Hornstzirom .S, and Radnoczi ,G.(1987), Al- Sb doped polycrystalline Si by the metal-induced crystallization, J.Appl.phys ,62 ( 9): 3726-3727. 2- Youngkim ,R. and Gikim ,H .(2007), The deposition of Sb/Ge films by metal organic chemical vapor deposition, J.of Appl.phys,102, 083531,1-4. 3- Sze, S. M. (2001), Semiconductor Devices: Physics and Technology. 2nd ed. New York: John Wiley and Sons, unipolar devices, 221-222. 4- Milnes,A.G.and Feucht .D.L, (1972), Heterojunction and Metal-Semiconductors Junctions,Academic Press, Newyork and London. 5- Wang ,Y.; Biest ,O.; Leuven ,K.; Arenberg and Gordon , (2005), 20th Europea Photovoltaic Solar Energy Conference, 1179-1181. 6- Fang, Y.K. Yang. (1989), The effect of heat temperature on the electrical resistivity of Sb deposited by means of molecular beam on Si, Thin solid films, 176, (1) ,91-97. 7- Ahssan, H.S. (2009), Electronic Transport Mechanicm of Se/c-Si Diode, M.Sc. thesis, Baghdad Univ. 8-Sinha, N.P. and Mirsa, M. (1983),Electrical properties of Si films doped Sb by molecular beam epitaxy, Solid-State Electronics,26 (12):1170 –1180. 9- Hobart ,K. Godbey. D and Thompson, (1992), post-growth annealing of low temperature-grown Sb-doped Si molecular beam epitaxial films, Appl.phys.Lett, 61(1):76-78 155 | Physics @1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 Table (1): The structural parameters of Sb film Ta (K) 2θ d (Å)Exp d(Å)Std. hkl RT 23.709 3.749 3.753 (003) 42.08 2.145 2.152 (110) 48.479 1.876 1.87 (006) 473 23.673 3.755 3.753 (003) 42.003 2.149 2.152 (110) 48.487 1.876 1.87 (006) Table (2): Values of ideality factor (β), saturation current (Is) and potential barrier height (Фb) for Sb/c-Si hetero junction with thickness 0.25μm and annealing temperatures (RT, 473k). Fig.( 1): XRD of Sb with different annealing temperatures (a):as deposited(303K) (b):Ta=473K Thickness (µm) Ta (K) β Is (μA) Фb(eV) 0.25 R.T 3.262 0.145 0.825 473 2.71 0.071 0.844 (a) (b) 156 | Physics @1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 Fig. (2): I-V characteristics in the dark for Al/c-Si at forward and reverse bias voltage with thickness(0.25μm) and annealing temperatures (RT,473K) Fig. (3): I-V characteristics in the dark for Sb/c-Si heterojunction at forward and reverse bias voltage with thickness(0.25μm) and annealing temperatures (RT,473K) I(𝝁𝝁 A ) V(volt) ٤٫۳ ۳٫۸ ۳٫٥ ۳ ۲٫٥ ۲ I( μA ) v(Volt) Ta=RT Ta=473k 157 | Physics @1a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹26@@ÖÜ»€a@I1@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (1) 2013 Al/c-Si و Sb/c-Si جھد لمفرق -مقارنة خصائص تیار فاتن گاصد حاچم ي قارذجامعة /كلیة العلوم / قسم الفیزیاء رامز احمد االنصاري جامعة بغداد / كلیة العلوم للبنات / قسم الفیزیاء حسین خزعل الالمي جامعة بغداد / كلیة العلوم / قسم الفیزیاء 2012ایار 21قبل البحث في ، 2012اذار 15استلم البحث في : الخالصة n-typeاحادي البلورة مفرق ھجین من ترسیب أغشیة االنتیمون وااللمنیوم على رقائق من السلیكون تم تحضیر K 473 ثم لدنت العینات بدرجة حراره , Å/sec 2.77 وبمعدل ترسیب (0.25µm) بطریقة الترسیب بالفراغ بسمك الجھد في تعددة التبلور، ووجد ارتفاع حاجزأظھرت الفحوصات ان جمیع اغشیة االنتیمون ذو تركیب م مدة ساعة واحدة. كانت أومیھ وفسر ذلك لعدم وجود حاجز جھد I-Vقیاس خواص لوحظ ان Al/c-Siلمفرق. Sb/c-Si .825eVمفرق . ,Al Siمن (Sb /Si) خصائص فولتیة تیار ،(Sb)الخواص التركیبیة لالنتیمون، (Sb/Si) :المفرق الھجینالكلمات المفتاحیة 158 | Physics