Origin of high oscillator strength in green-emitting InGaN/GaN nanocolumns
Origin of high oscillator strength in green-emitting InGaN/GaN nanocolumns
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DOI：
10.1063/1.2363958
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发表时间：
2006-10-16
影响因子：
4
通讯作者：
Kishino, K.
中科院分区：
文献类型：
--
作者：
Kawakami, Y.;Suzuki, S.;Kishino, K.
对氮等离子体辅助分子束外延生长的InGaN/GaN纳米柱结构进行了光学表征，不仅在宏观结构上，而且在微观结构上，可以评估到单个纳米柱。在500 nm处测得的光致发光（PL）衰减符合双指数曲线，其寿命在13 K时分别为0.67和4.33 ns。这些值比在朝向C取向生长的常规InGaN/GaN量子威尔斯（QW）中在相同波长处所取的值小两个数量级。使用机械剥离技术实现每个单个纳米柱的PL检测。结果表明，宏观上观察到的非常宽的PL谱是由于来自每个纳米柱的尖锐PL谱的总和，其峰值能量波动。此外，与传统量子阱不同，在较高的光激发下，单个纳米柱的蓝移小得可以忽略不计。这些发现表明，载流子本地化以及压电极化场被抑制在InGaN/GaN纳米柱。
Optical characterization has been performed on an InGaN/GaN nanocolumn structure grown by nitrogen plasma assisted molecular beam epitaxy not only in macroscopic configuration but also in a microscopic one that can be assessed to a single nanocolumn. The photoluminescence (PL) decay monitored at 500 nm is fitted with a double exponential curve, which has lifetimes of 0.67 and 4.33 ns at 13 K. These values are two orders of magnitude smaller than those taken at the same wavelength in conventional InGaN/GaN quantum wells (QWs) grown toward the C orientation. PL detection of each single nanocolumn was achieved using a mechanical lift-off technique. The results indicate that the very broad, macroscopically observed PL spectrum is due to the sum of the sharp PL spectrum from each nanocolumn, the peak energy of which fluctuates. Moreover, unlike conventional QWs, the blueshift of a single nanocolumn is negligibly small under higher photoexcitation. These findings suggest that carrier localization as well as the piezoelectric polarization field is suppressed in InGaN/GaN nanocolumns.