Interface structural defects and photoluminescence properties of epitaxial GaN and AlGaN/GaN layers grown on sapphire
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UCTOR STRUCTURES, INTERFACES, AND SURFACES
Interface Structural Defects and Photoluminescence Properties of Epitaxial GaN and AlGaN/GaN Layers Grown on Sapphire V. P. Klad’koa, S. V. Chornen’kiia, A. V. Naumova^, A. V. Komarovb, M. Tacanoc, Yu. N. Sveshnikovd, S. A. Vitusevicha, and A. E. Belyaeva aLashkarev
Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, Kiev, 03028 Ukraine ^e-mail: [email protected] bInstitute of Physics, National Academy of Sciences of Ukraine, Kiev, 03028 Ukraine cAMRC, Meisei University, Hino, Tokyo, 191-8506 Japan dZAO 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 determined. 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
1. INTRODUCTION The progress of the present-day semiconductor physics and technology, specifically quantum electronics and optoelectronics depends to a large extent on the technology of high-quality semiconductor materials and the development of perfect epitaxial heterostructures with specified physical properties [1, 2]. The high quality of such heterostructures (HSs) is defined primarily 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 heterointerface 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 dislocations. In addition to the increase in the density of dislocations, nonuniformities in their distribution in the heterointerface 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 parameters are modified. Therefore, there is some correlation between the structural characteristics (m
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