Direct observation of lattice constant variations depending on layer structures in an InGaN/GaN MQW LED

Shigeya Kimura; Koichi Tachibana; Toshiyuki Oka; Hajime Nago; Hisashi Yoshida; Shinya Nunoue

doi:10.1117/12.874626

3 March 2011 Direct observation of lattice constant variations depending on layer structures in an InGaN/GaN MQW LED

Shigeya Kimura, Koichi Tachibana, Toshiyuki Oka, Hajime Nago, Hisashi Yoshida, Shinya Nunoue

Proceedings Volume 7939, Gallium Nitride Materials and Devices VI; 79392D (2011) https://doi.org/10.1117/12.874626
Event: SPIE OPTO, 2011, San Francisco, California, United States

Abstract

We have directly observed that InGaN quantum well layers were incoherently grown on 5-nm-thick GaN barrier layers in an InGaN/GaN multiple quantum well (MQW) system of a blue light-emitting diode by using a lattice image obtained by high-resolution transmission electron microscopy and fast Fourier transform mapping (FFTM) analysis of the lattice image. The lattice disorder was observed in the middle of the InGaN well layer by using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). In contrast, FFTM of the InGaN well layers with 10-nm-thick barrier layers showed the intervals of the (01-10) lattice planes were homogeneous, and the lattice disorder was not observed in the HAADF-STEM image. These results indicate that the excess stain in the InGaN/GaN MQW having thinner GaN barrier layers induces the lattice disorder in the InGaN well layers. Indium composition fluctuation in the InGaN well layer was also observed by using three-dimensional atom probe analysis. It indicates that the incorporation of indium atoms is affected by the imperfect structural properties of the MQW system with thinner GaN barrier layers. The intensity of electroluminescence from the sample with 10-nm-thick barrier layers in the MQWs was higher than that from the sample with 5-nm-thick barrier layers.

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Shigeya Kimura, Koichi Tachibana, Toshiyuki Oka, Hajime Nago, Hisashi Yoshida, and Shinya Nunoue "Direct observation of lattice constant variations depending on layer structures in an InGaN/GaN MQW LED", Proc. SPIE 7939, Gallium Nitride Materials and Devices VI, 79392D (3 March 2011); https://doi.org/10.1117/12.874626

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