Solid State Communications 149 (2009) 337–340 Contents lists available at ScienceDirect Solid State Communications journal homepage: www.elsevier.com/locate/ssc Anomalous temperature dependence of the electrical resistivity in In 0.17 Ga 0.83 N A. Yildiz a,∗ , S.B. Lisesivdin b , M. Kasap b , M. Bosi c a Department of Physics, Faculty of Science and Arts, Ahi Evran University, Aşıkpaşa Kampüsü, 40040, Kirsehir, Turkey b Department of Physics, Faculty of Science and Arts, Gazi University, Teknikokullar, 06500, Ankara, Turkey c CNR-IMEM Institute, Area delle Scienze 37/A, I-43010 Fontanini, Parma, Italy article info Article history: Received 10 January 2008 Received in revised form 21 October 2008 Accepted 22 November 2008 by E.V. Sampathkumaran Available online 3 December 2008 PACS: 72.20.Fr 71.55.Eq Keywords: E. InGaN F. Electronic transport abstract Resistivity and Hall effect measurements on n-type undoped In 0.17 Ga 0.83 N alloy grown by metal- organic vapor phase epitaxy (MOVPE) technique were carried out as a function of temperature (15–350 K). In 0.17 Ga 0.83 N alloy is regarded as a highly degenerate semiconductor system with a high carrier concentration of ∼9.2 × 10 19 cm −3 . An anomalous resistivity behavior is observed over the whole temperature range. The temperature dependent resistivity of In 0.17 Ga 0.83 N exhibits a metal- semiconductor transition (MST) around 180 K. The temperature coefficient of resistivity is negative at low temperatures (T < 180 K) and it becomes positive at relatively high temperatures (T > 180 K). In addition to this, a negative magnetoresistivity (MR) has been observed below 180 K. The temperature dependent resistivity of In 0.17 Ga 0.83 N alloy is explained in the terms of the electron–electron interaction (EEI) and the weak localization (WL) phenomenon at low temperatures (T < 180 K). At high temperatures (T > 180 K) the temperature dependent resistivity obeys T 2 law. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction The In x Ga 1−x N material system with high Ga composition has attracted a great deal of attention in recent years. It is used as an active layer in blue and green light emitting diodes and lasers [1– 4]. In spite of numerous studies having been carried out on the optical and structural properties of In x Ga 1−x N[5,6], studies on the electrical transport properties of this material system are still limited due to difficulty in controlling the conductivity. Since the growth temperature of In x Ga 1−x N is generally lower than that of GaN, the decomposition rate of ammonia (NH 3 ) becomes low at low-growth temperatures [7]. The low temperature growth conditions cause an increment in number of nitrogen vacancies. Nitrogen vacancies increment results a high background carrier concentration in undoped In x Ga 1−x N alloy. At sufficiently high impurity concentrations, the electron transport in semiconductors exhibits metallic behavior above the critical Mott concentration (n c ). In fact, impurity conduction may become significant even at high temperatures in high energy gap Ga-rich In x Ga 1−x N alloys in which compensation is nearly full. As can be seen from the literature, InN and related alloys can exhibit metallic impurity band conduction with a high carrier concentration and in this case they have low mobility values. ∗ Corresponding author. Tel.: +90 386 252 80 50; fax: +90 386 252 80 54. E-mail address: yildizab@gmail.com (A. Yildiz). For the InN with electron concentrations of more than 1 × 10 19 cm −3 , mobility is normally less than 250 cm 2 /Vs [8,9]. Lin et al. [10] observed that the electron concentration in In x Ga 1−x N films is temperature independent over a wide temperature range 4K ≤ T ≤ 285 K. Their experimental results demonstrated that the electron transport in In-rich In x Ga 1−x N films with a carrier concentration ∼2 × 10 19 cm −3 show metallic behavior. Geerstet al. [11] studied carrier transport phenomena in n-type In x Ga 1−x N with variable temperature (1.7–400 K) and magnetic field (0–30 T) Hall measurements. Their In 0.18 Ga 0.82 N sample (n ∼ 4 × 10 19 cm −3 and µ ∼ 3 cm 2 /Vs) showed metallic conduction, which due to intrinsic shallow donors in In x Ga 1−x N material. They also observed that the In 0.18 Ga 0.82 N shows a negative magnetoresistance over a wide temperature range (2–350 K) [11]. In the metallic side of the metal-insulator transition, the re- sistivity of a highly degenerate semiconductor decreases with de- creasing temperature as is typical for a good metal. However, the resistivity of a highly degenerate semiconductor can exhibit anomalous behavior at low temperatures, as structural or com- positional disorder increases in the material. In such a material, the mean free path between collisions becomes small and quan- tum effects become important. If the resistivity of highly degener- ate semiconductors increases with decreasing temperature at low temperatures, the Boltzmann approach may not successfully de- scribe the transport properties of the material [12]. This requires quantum corrections to the Boltzmann conductivity. It is widely ac- cepted that the electron transport properties of such materials can 0038-1098/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2008.11.026