Structural and Optical Studies of InGaN/GaN Superlattices Implanted with Eu Ions
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Structural and Optical Studies of InGaN/GaN Superlattices Implanted with Eu Ions Jingzhou Wang1, Venkata R. Thota2, Eric A. Stinaff2, Mohammad Ebdah3, Andre Anders4 and Wojciech M. Jadwisienczak1 1 School of Electrical Engineering and Computer Science, Ohio University, Athens OH 45701, U.S.A. 2 Department of Physics and Astronomy, Ohio University, Athens, OH 45701, U.S.A. 3 Physics and Astronomy Department, King Saud University, Saudi Arabia. 4 Lawrence Berkeley National Laboratory, Plasma Applications Group, Berkeley, CA 94720, U.S.A. ABSTRACT In0.06Ga0.94N/GaN superlattices (SLs) grown on sapphire (0001) by metalorganic chemical vapor deposition were studied before and after europium (Eu) ion implantation to understand the strain induced-effects in the SL structure. The implanted SLs were investigated as a function of the thermal annealing temperature up to 1000 C in nitrogen ambient. Temperature dependent photoluminescence spectra showed a red-shift of the SL emission peaks due the quantum confined Stark effect, followed by a blue-shift due to In atoms out-diffusion from the In0.06Ga0.94N quantum well, for both Eu ions implanted and unimplanted SLs. The amplitude of observed spectral shifts was smaller and the line width of the SLs emission peaks were narrower in the SLs:Eu3+ as compared to the unimplanted SLs. It is concluded that Eu3+ ions modified the strain in the SLs acting like impurity and/or defects getter in implantation degraded SLs resulting in material phase purification and improvements of SLs optical properties. INTRODUCTION Rare earth (RE)-doped III-nitride (III-N) semiconductors have attracted much attention as prospective materials for optoelectronics and spintronics in the UV, visible and near IR spectral regions [1]. Recently, europium doped III-Ns were extensively investigated due to the prospect of developing a red color emitter required for fabricating monolithic red-green-blue (RGB) III-Ns displays [2–4]. This approach offers an alternative route to overcome the current technological pitfalls due to the difficulties in growing InxGa1-xN layers with high indium (In) content resulting in degraded crystal quality and the presence of a high internal piezoelectric field. It is also known that the RE3+ ions radiative quantum efficiency strongly depends on carrier mediated energy transfer processes, which must compete with non-radiative recombination channels typically abundant in the III-Ns. Thus, RE-doping into III-Ns quantum structures may enhance radiative emission from RE3+ ions due to better carrier localization in low dimensional structures. It was demonstrated that Eu3+ ion can be incorporated into the InGaN/GaN quantum wells (QWs) [5–7] or in AlGaN/GaN multi-quantum wells (MQWs) [8,9], respectively. However, similar studies in Eu-doped InGaN/GaN SLs are limited. In this paper, we study the quality evolution of In0.06Ga0.94N/GaN SL interfaces upon europium ion implantation as a function of post-implantation annealing temperature. Theoretical simulations were performed to reproduce the exp
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