不同极性核壳纳米棒中 InGaN/GaN 量子阱的局域化和瞬态发射特性。

Localization and transient emission properties in InGaN/GaN quantum wells of different polarities within core-shell nanorods.

机构信息

Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Japan.

出版信息

Nanoscale. 2018 Dec 20;11(1):193-199. doi: 10.1039/c8nr05863f.

Abstract

Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K. The NRs exhibit three well-defined PL bands in the near-UV, blue, and green range ascribed to the emission of quantum well (QW) areas situated at the (1.00) sidewalls, (10.1) top facets, and (00.1) tip, respectively. At low temperature, time-resolved PL shows a fast decay time of about 0.5 ns for the semi- and non-polar QWs, while the polar QWs exhibit at least a twice-longer time. Rapid delocalization of carriers above 50 K indicates shallow potential fluctuations in the QWs. At room temperature, the characteristic fast PL decay time of the three QW bands stabilizes around 300 ps. The slow decaying PL components have different characteristic decay times that are explained by additional localization at basal stacking faults (BSFs), taking into account the quantum confined Stark effect. In addition, narrow excitonic luminescence lines are observed in the BSF-enriched polar QWs, providing direct evidence of the impact of the BSF/QW crossings on the optical properties of the NRs. A PL rise time of about 100 ps does not show any deviation between bands. These findings are suggestive of similar transport mechanisms in temperature equilibrium without inter-facet transport between different QWs. We believe that predictable transient characteristics can play a key role in creating uniform NR ensembles for device applications.

摘要

从 6 K 到 285 K，研究了 InGaN/GaN 核壳纳米棒（NRs）中的瞬态光致发光（PL）特性和局域化现象。NRs 在近紫外、蓝色和绿色范围内表现出三个定义明确的 PL 带，归因于位于（1.00）侧壁、（10.1）顶面上和（00.1）尖端的量子阱（QW）区域的发射。在低温下，时间分辨 PL 显示半极性和非极性 QW 的快速衰减时间约为 0.5 ns，而极性 QW 的衰减时间至少长两倍。在 50 K 以上，载流子的快速离域表明 QW 中的势阱浅波动。在室温下，三个 QW 带的特征快速 PL 衰减时间稳定在 300 ps 左右。慢衰减 PL 分量具有不同的特征衰减时间，这可以通过在考虑量子限制斯塔克效应的情况下，在基底堆垛层错（BSF）处进行额外的局域化来解释。此外，在富含 BSF 的极性 QW 中观察到窄激子发光线，为 BSF/QW 交叉对 NRs 光学性质的影响提供了直接证据。PL 上升时间约为 100 ps，各带之间没有任何偏差。这些发现表明在温度平衡中存在类似的传输机制，不同 QW 之间没有界面传输。我们相信，可预测的瞬态特性可以在为器件应用创建均匀的 NR 组件方面发挥关键作用。