ISSN 1063-7826, Semiconductors, 2015, Vol. 49, No. 4, pp. 461–471. © Pleiades Publishing, Ltd., 2015. Original Russian Text © A.V. Sachenko, A.E. Belyaev, N.S. Boltovets, P.N. Brunkov, V.N. Jmerik, S.V. Ivanov, L.M. Kapitanchuk, R.V. Konakova, V.P. Klad’ko, P.N. Romanets, P.O. Saja, N.V. Safryuk, V.N. Sheremet, 2015, published in Fizika i Tekhnika Poluprovodnikov, 2015, Vol. 49, No. 4, pp. 472–482. 461 1. INTRODUCTION In the last few years, indium nitride and alloys on its basis have been the most actively studied materials among nitrides of Group-III elements. Interest in them is due to promising applications in the develop- ment of some active elements for opto-, spin-, and microwave electronics [1–4]. The specific feature of these materials is their epitaxial growth technology. The point is that there is no substrate material for them, as well as for other III–N compounds, which would be suitable for commercial production; there- fore, InN and alloys on its basis are grown as hetero- structures with buffer layers. As substrates, Al 2 O 3 , GaAs, Si, and fianites are used. Due to the mismatch of the lattice parameters and thermal expansion coef- ficients of the InN film and substrate (e.g., Al 2 O 3 ), internal mechanical stresses arise in heterostructures, whose relaxation leads to the generation of disloca- tions with densities from 10 8 to 3 × 10 11 cm –2 . This cannot but affect the parameters of corresponding devices, first and foremost, the characteristics of ohmic contacts to them. Indeed, as shown in [5–7], the contact resistivity ρ c of ohmic contacts to semiconductors with high dislo- cation densities and its temperature dependence ρ c (T) depend heavily on the dislocation density, if the con- tact-forming metal (alloy) or metal from other contact metallization layers penetrates into the thin near-con- tact semiconductor layer via dislocations during ohmic-contact formation, forming metal shunts in it. Furthermore, as shown in [8], in layers of InN, due to its thermodynamic instability and the specificity of epitaxial growth near the transition to surface enrich- ment with the metal, the formation of metal In precip- itates and In accumulation at dislocations is highly probable. This can also cause the formation of metal shunts in InN layers. The dependence ρ c (T) at rather high temperatures can be an increasing dependence. In this case, ρ c increases with measurement temperature and, in the region of operating temperatures, can appreciably exceed ρ c measured at room temperature. Goldberg et al. (see, e.g., [5]) proposed an explanation of the increasing dependences ρ c (T) by the temperature dependence of the metal-shunt resistance. However, the proposed explanation does not describe the depen- dence ρ c (T) in a rather wide range of temperature measurements. For example, in the region of rather low temperatures, the dependences ρ c (T) are either decreasing or independent of temperature. The behav- ior of the experimental dependences ρ c (T) in semi- SEMICONDUCTOR STRUCTURES, LOW-DIMENSIONAL SYSTEMS, AND QUANTUM PHENOMENA Temperature Dependences of the Contact Resistivity in Ohmic Contacts to n + -InN A. V. Sachenko a , A. E. Belyaev a , N. S. Boltovets b , P. N. Brunkov c, d , V. N. Jmerik c , S. V. Ivanov c , L. M. Kapitanchuk e , R. V. Konakova a ^, V. P. Klad’ko a , P. N. Romanets a , P. O. Saja a , N. V. Safryuk a , and V. N. Sheremet a a Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 41, Kyiv, 03028 Ukraine ^e-mail: konakova@isp.kiev.ua b “Orion” Research Institute, vul. E. Pottier 8a, Kyiv, 03057 Ukraine c Ioffe Physical–Technical Institute, Russian Academy of Sciences, ul. Politekhnicheskaya 26, St. Petersburg, 194021 Russia d National Research University of Information Technologies, Mechanics and Optics, pr. Kronverkskii 49, St. Petersburg, 197101 Russia e Paton Electric Welding Institute, National Academy of Sciences of Ukraine, vul. Bozhenko 11, Kyiv, 03680 Ukraine Submitted July 31, 2014; accepted for publication September 4, 2014 Abstract—The temperature dependences of the contact resistivity (ρ c ) of ohmic contacts based on the Au–Ti–Pd–InN system are measured at an InN doping level of 2 × 10 18 cm –3 in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ c (T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislo- cations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive disloca- tions is ~5 × 10 9 cm –2 . Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10 10 cm –2 . DOI: 10.1134/S1063782615040193