The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem
The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem
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DOI：
10.1016/j.ultramic.2017.01.019
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发表时间：
2017-05-01
期刊：
影响因子：
2.2
通讯作者：
Oliver, R. A.
中科院分区：
文献类型：
--
作者：
Humphreys, C. J.;Griffiths, J. T.;Oliver, R. A.
利用高分辨率透射电子显微镜（HRTEM）、像差校正定量扫描透射电子显微镜（Q-STEM）、原子探针层析成像（APT）和x射线衍射（XRD）研究了（0001）极性和（11-20）非极性InGaN量子阱（QWs）的原子结构。本文概述了研究结果。qw中的极性（0001）InGaN是一种随机合金，in随机替换Ga。InGaN量子阱具有原子高度界面阶跃，导致量子阱宽度波动。电子通过内置电场和井宽波动定位在顶部量子阱界面，定位能量通常为20meV。由于随机合金中铟的波动，这些空穴被定位在底部量子阱界面附近，定位能量通常为60meV。另一方面，非极性（11-20）InGaN量子阱含有纳米级的富铟团簇，我们认为这些团簇可以定位载流子并产生比具有相同平均成分的随机合金非极性InGaN量子阱更长的波长（更低的能量）发射。非极性（11-20）InGaN QW中富铟团簇的原因尚不清楚，但可能与（11-20）InGaN QW的QW生长温度较（0001）极性InGaN QW低有关。(C) 2017年作者。Elsevier B.V.出版
We have used high resolution transmission electron microscopy (HRTEM), aberration-corrected quantitative scanning transmission electron microscopy (Q-STEM), atom probe tomography (APT) and X-ray diffraction (XRD) to study the atomic structure of (0001) polar and (11-20) non-polar InGaN quantum wells (QWs). This paper provides an overview of the results. Polar (0001) InGaN in QWs is a random alloy, with In replacing Ga randomly. The InGaN QWs have atomic height interface steps, resulting in QW width fluctuations. The electrons are localised at the top QW interface by the built-in electric field and the well-width fluctuations, with a localisation energy of typically 20meV. The holes are localised near the bottom QW interface, by indium fluctuations in the random alloy, with a localisation energy of typically 60meV. On the other hand, the non-polar (11-20) InGaN QWs contain nanometre-scale indium rich clusters which we suggest localise the carriers and produce longer wavelength (lower energy) emission than from random alloy non-polar InGaN QWs of the same average composition. The reason for the indium-rich clusters in non-polar (11-20) InGaN QWs is not yet clear, but may be connected to the lower QW growth temperature for the (11-20) InGaN QWs compared to the (0001) polar InGaN QWs. (C) 2017 The Authors. Published by Elsevier B.V.