ISSN 1063-7826, Semiconductors, 2006, Vol. 40, No. 9, pp. 1060–1065. © Pleiades Publishing, Inc., 2006. Original Russian Text © V.P. Klad’ko, S.V. Chornen’kii, A.V. Naumov, A.V. Komarov, M. Tacano, Yu.N. Sveshnikov, S.A. Vitusevich, A.E. Belyaev, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 9, pp. 1087–1093. 1060 1. INTRODUCTION The progress of the present-day semiconductor physics and technology, specifically quantum electron- ics and optoelectronics depends to a large extent on the technology of high-quality semiconductor materials and the development of perfect epitaxial heterostruc- tures with specified physical properties [1, 2]. The high quality of such heterostructures (HSs) is defined prima- rily by the minimal elastic strains and the absence of plastic strains in the active (working) region, while the efficiency and reliability of operation of HS-based devices depend on the localization and density of active impurity defects and structural defects at the heteroint- erface and in the working region. In the course of epitaxial growth, the heterolayers and films can be matched to the technological wafer coherently or incoherently. In the case of the coherent (so-called pseudomorphic) growth of the starting layer, the mismatch of the lattice parameters of the film and wafer does not give rise to misfit dislocations. Under deviations from the conditions of coherent growth with increasing film thickness, relaxation of elastic strains in the system gives rise to misfit disloca- tions. In addition to the increase in the density of dislo- cations, nonuniformities in their distribution in the het- erointerface plane appear. Plastic strain resulting from of uncompensated stresses and linear structural defects in the system is the final consequence of the incoherent growth. In this case, the semiconductor properties of the system prescribed by the initial alloy composition and, hence, by the mismatch between the lattice param- eters are modified. Therefore, there is some correlation between the structural characteristics (mismatch between the lattice parameters, elastic stresses, and plastic strain) of epitaxial HSs and the physical proper- ties and parameters such as the band gap, the half-width and peak energy of the edge luminescence band, the quantum yield of radiative recombination, the character of polarization of the emission, etc. [3]. In the last few years, HSs based on the III-Group nitrides have attracted considerable interest. Such HSs are widely used for the development of injection lasers and light-emitting diodes for the short-wavelength region of the spectrum. These HSs are thought to be promising for applications in high-voltage microelec- tronics and high-frequency microelectronics [4]. Spe- cifically, GaN-based HSs (due to the wide band gap and high drift velocities) are considered as the most appro- priate structures for developing field-effect transistors operating by high-mobility hot electrons (often referred to as high electron mobility transistors (HEMTs)) [5]. The GaN/AlGaN HSs are commonly grown from metal organic compounds by gas-phase epitaxy, i.e., by metal-organic chemical vapor deposition (MOCVD) on sapphire wafers in reactors with inductive heating [6]. The sources of the Ga, Al, and N elements are trimethyl gallium (TMG), trimethyl aluminum (TMA), and ammonia (NH 3 ); for doping, silane (SiH 4 ) is used, and hydrogen serves as a gas carrier. At first, a thin layer of GaN or of GaN with an admixture of Al is deposited on SEMICONDUCTOR STRUCTURES, INTERFACES, AND SURFACES Interface Structural Defects and Photoluminescence Properties of Epitaxial GaN and AlGaN/GaN Layers Grown on Sapphire V. P. Klad’ko a , S. V. Chornen’kii a , A. V. Naumov a ^, A. V. Komarov b , M. Tacano c , Yu. N. Sveshnikov d , S. A. Vitusevich a , and A. E. Belyaev a a Lashkarev Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, Kiev, 03028 Ukraine ^e-mail: naumov@ifpht.kiev.ua b Institute of Physics, National Academy of Sciences of Ukraine, Kiev, 03028 Ukraine c AMRC, Meisei University, Hino, Tokyo, 191-8506 Japan d ZAO Élma–Malakhit, Zelenograd, 124460 Russia Submitted January 11, 2006; accepted for publication January 25, 2006 Abstract—Overall characterization of the GaN and AlGaN/GaN epitaxial layers by X-ray diffractometry and optical spectral analysis is carried out. The layers are grown by metalloorganic gas-phase epitaxy on (0001)- oriented single crystal sapphire wafers. The components of strains and the density of dislocations are deter- mined. The effects of strains and dislocations on the photoluminescence intensity and spectra are studied. The results allow better understanding of the nature and mechanisms of the formation of defects in the epitaxial AlGaN/GaN heterostructures. PACS numbers: 61.10.Nz, 68.35.Ct, 68.55Jk, 78.55.Cr DOI: 10.1134/S1063782606090132