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TRONIC AND OPTICAL PROPERTIES OF SEMICONDUCTORS

Temperature Dependence of the Band Structure of Wurtzite-Type Semiconductor Compounds: Gallium and Aluminum Nitrides T. V. Gorkavenkoa^, S. M. Zubkovab, and L. N. Rusinab aDepartment

of Physics, Shevchenko National University, Kiev, 03022 Ukraine ^e-mail: [email protected] bFrantsevich Institute of Materials Science Problems, National Academy of Sciences of Ukraine, Kiev, 03680 Ukraine Submitted September 27, 2006; accepted for publication October 2, 2006

Abstract—The method of empirical pseudopotential was used for the first time for the calculation of the temperature dependence of the energy extrema at the Γ, L, K, M, A, and H high-symmetry points of the Brillouin zone for hexagonal modifications of gallium and aluminum nitrides, as well as of the energies of the main interband transitions between these extrema. The effect of the temperature dependence of electron–phonon interaction on the band structure of the crystal was described using the Debye–Waller factors, and the contribution of the linear expansion of the lattice was taken into account via the temperature dependence of the linear expansion coefficient. The features of the temperature dependence of the energy levels and interband transitions were analyzed in detail. Comparison of the calculations with the experimental data in available publications has shown good agreement. PACS numbers: 71.20.Nr DOI: 10.1134/S106378260706005X

1. INTRODUCTION Over the last 15 years, in many laboratories of Germany, Japan, USA, Russia, Poland, China, and other countries, intensive theoretical and experimental studies of nitrides of Group III elements (GaN, AlN, InN) in the form of single crystals, thin films, alloys, and heterostructures on their basis have been carried out. This circumstance is related to the remarkable electrical and optical properties of these crystals required for their applications, first of all, in optoelectronics and microelectronics, and also in laser technology. For example, GaN has wurtzite structure, direct band gap near the ultra-violet (UV) region (~3.4 eV), has chemical and radiation stability, forms chemical bonds that are ~20% shorter than for most semiconductors, and has a high ionicity degree, high hardness, high heat conductivity, and high electron mobility. It can form solid solutions with AlN and InN, thus making it possible to control the electronic and optical properties of its crystals. Due to these features, GaN has in recent years become widely used in optoelectronics and microelectronics for the fabrication of high-quality blue lightemitting diodes used to obtain the third primary color in semiconductor-based displays, UV light-emitting diodes, UV sensor controls, short-wavelength laser diodes for applications in optical systems for data accumulation, pulse and continuous lasers operating in the blue and

UV spectral regions, high electron mobility transistors, high-frequency devices (due to small transport times), and UV photoconductors. On the basis of GaN, highquality contact