Effect of Deuterium Diffusion on the Electrical Properties of AlGaN/GaN Heterostructures
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E9.31.1
Effect of deuterium diffusion on the electrical properties of AlGaN/GaN heterostructures Jaime Mimila Arroyo 1*, Michel Barbé 1, François Jomard 1, Dominique Ballutaud 1, Jacques Chevallier 1 , Marie-Antoinette Poisson 2, Sylvain Delage 2, Christian Dua 2, Yvon Cordier 3, Maxime Hugues 3, Fabrice Semond 3, Franck Natali 3, Philippe Lorenzini 3, Jean Massies 3 1 Laboratoire de Physique des Solides et de Cristallogénèse, UMR CNRS 8635, 1 place A.Briand, 92195 Meudon Cedex, France. 2 Thales Research and Technology, Domaine de Corbeville, 91404 Orsay Cedex, France. 3 Centre de Recherche sur l’Hétéro-Epitaxie et ses Applications, Parc de Sophia-Antipolis, Rue B.Grégory, 06560 Valbonne, France. ABSTRACT We have studied the influence of a deuterium diffusion on the electrical characteristics of the 2D gas present in AlGaN/GaN heterostructures. The deuterium diffusion is performed by exposing the structures to a rf remote deuterium plasma. We find that both the sheet carrier concentration and the electron mobility decrease and that these effects are partly reversible under thermal annealing. These results suggest that deuterium behave as acceptors in the 2D gas region. The negatively charged deuterium act as additional scattering centers for electrons. INTRODUCTION AlGaN/GaN high electron mobility transistors (HEMTs) have been the subject of intense investigations because, due to their high breakdown voltage and their excellent transport properties, they offer a strong potential for use in high power solid state microwave applications. However, presently, these devices suffer from reliability problems and it has been reported that current collapse occurs in these devices after applications of a high drain-source voltage [1-3]. This effect has been attributed to trapping of carriers by surface states and by defects in the active layer [3,4]. In addition, defects are a source of noise generation in field effect transistors [5]. It is established that hydrogen has the ability to passivate deep levels and dopants in a number of semiconductors and the passivation of magnesium acceptors in GaN is a well known example [6,7]. In addition, it has been shown that, under post-hydrogenation, certain defects are passivated in n-GaN |8,9]. For this reason, it is interesting to investigate the influence of the controlled introduction of hydrogen (deuterium) on the properties of the AlGaN/GaN heterostructures as hydrogen might passivate some of the defects and consequently improve the reliability and performances of HEMTs. In this work, we report on the effect of deuterium diffusion on the electrical properties of the 2D electron gas present at the AlGaN/GaN interface. EXPERIMENTAL The AlGaN/GaN heterostructures used for our investigations were grown either by molecular beam epitaxy (MBE) on resistive (>10 kOhm.cm) (111) silicon substrates (namely 392 and 545) or by metal organic chemical vapour deposition (MOCVD) on n+-SiC substrates (namely 999). Their structure is composed of an adapting layer, a GaN buffer layer, a AlxGa1-xN l
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