The Influence of Growth Temperature on Oxygen Concentration in GaN Buffer Layer
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1068-C03-09
The Influence of Growth Temperature on Oxygen Concentration in GaN Buffer Layer Ewa Dumiszewska1,2, Wlodek Strupinski1, Piotr Caban1,3, Marek Wesolowski1, Dariusz Lenkiewicz1,2, Rafal Jakiela1,4, Karolina Pagowska5, Andrzej Turos1,5, and Krzysztof Zdunek2 1 III-V Epitaxy Department, Institute of Electronic Materials Technology, Wolczynska 133, Warsaw, 01-919, Poland 2 Faculty of Materials Science, Warsaw University of Technology, Woloska 141, Warsaw, 02507, Poland 3 Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Nowowiejska 15/19, Warsaw, 00-665, Poland 4 Institute of Physics, Polish Academy of Sciences, Lotnikow 32/46, Warsaw, Poland 5 Soltan Institute for Nuclear Studies, Swierk/Otwock, 05-400, Poland ABSTRACT The influence of growth temperature on oxygen incorporation into GaN epitaxial layers was studied. GaN layers deposited at low temperatures were characterized by much higher oxygen concentration than those deposited at high temperature typically used for epitaxial growth. GaN buffer layers (HT GaN) about 1 µm thick were deposited on GaN nucleation layers (NL) with various thicknesses. The influence of NL thickness on crystalline quality and oxygen concentration of HT GaN layers were studied using RBS and SIMS. With increasing thickness of NL the crystalline quality of GaN buffer layers deteriorates and the oxygen concentration increases. It was observed that oxygen atoms incorporated at low temperature in NL diffuse into GaN buffer layer during high temperature growth as a consequence GaN NL is the source for unintentional oxygen doping. Keywords: A1. MOVPE; A3 Gallium Nitride.; B1.Oxygen; INTRODUCTION Gallium nitride plays a significant role in optoelectronic and high-power, high frequency devices industry. Lack of commercially available free standing GaN substrates makes it necessary to use alternative ones such as sapphire (Al2O3), silicon carbide (SiC) or silicon. As the result, GaN layers grown on sapphire by the most commonly used method - metalorganic vapor phase epitaxy (MOVPE) are characterized by high oxygen concentration [1]. Oxygen in GaN layers influences n-type background conductivity and may be responsible for threading dislocation behavior [2,3]. Unfortunately, the origin of oxygen atoms is still not well understood. It was suggested that it was incorporated during the growth [3] or comes from sapphire substrate [4]. There are also numerous works indicating interactions between oxygen atoms and dislocations [3,5]. Liliental-Weber et al. [6] showed the increased nanopipes density at elevated oxygen content. Cherns et al. [7] claimed that oxygen may be responsible for electrical activity of dislocations. Our recent results also indicate that interaction between dislocations and oxygen atoms influences device performance [8]. There is a strong correlation between oxygen concentration and carrier concentration in high temperature (HT) GaN, i.e. the larger oxygen content, the higher carrier concentration. The aim of this work was the search for the
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