Correlative High‐Resolution Mapping of Strain and Charge Density in a Strained Piezoelectric Multilayer
Correlative High‐Resolution Mapping of Strain and Charge Density in a Strained Piezoelectric Multilayer
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DOI：
10.1002/admi.201400281
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发表时间：
2015
影响因子：
5.4
通讯作者：
K. Song;C. Koch;Ja Kyung Lee;Dong Yeong Kim;Jong Kyu Kim;A. Parvizi;W. Jung;Chan‐Gyung Park;H. J. Jeong;Hyoung Seop Kim;Ye Cao;Tiannan Yang;Long-Qing Chen;S. Oh
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文献类型：
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作者：
K. Song;C. Koch;Ja Kyung Lee;Dong Yeong Kim;Jong Kyu Kim;A. Parvizi;W. Jung;Chan‐Gyung Park;H. J. Jeong;Hyoung Seop Kim;Ye Cao;Tiannan Yang;Long-Qing Chen;S. Oh
压电半导体器件应变工程的关键是应变-电荷关系的定量评估。这在当前基于InGaN/GaN的发光二极管（LED）设计中尤其苛刻，因为已知压电效应会降低器件性能。利用最先进的在线电子全息技术，我们获得了传统蓝色led中二维应变张量和总电荷密度的完全定量图，并将其与亚纳米空间分辨率相关联。我们发现In0.15Ga0.85N量子阱沿极性生长方向压缩应变和拉长，对GaN量子势垒施加压缩应力/应变。直接从应变数据中获得极化梯度产生的界面片电荷，并与总电荷密度图进行比较，定量验证了只有60%的极化电荷被电子屏蔽，在每个In0.15Ga0.85N量子阱中留下了大量的压电场。所展示的在线电子全息技术为未来压电光电器件的应变工程提供了技术突破。
A key to strain engineering of piezoelectric semiconductor devices is the quantitative assessment of the strain‐charge relationship. This is particularly demanding in current InGaN/GaN‐based light‐emitting diode (LED) designs as piezoelectric effects are known to degrade the device performance. Using the state‐of‐the‐art inline electron holography, we have obtained fully quantitative maps of the two‐dimensional strain tensor and total charge density in conventional blue LEDs and correlated these with sub‐nanometer spatial resolution. We show that the In0.15Ga0.85N quantum wells are compressively strained and elongated along the polar growth direction, exerting compressive stress/strain on the GaN quantum barriers. Interface sheet charges arising from a polarization gradient are obtained directly from the strain data and compared with the total charge density map, quantitatively verifying only 60% of the polarization charges are screened by electrons, leaving a substantial piezoelectric field in each In0.15Ga0.85N quantum well. The demonstrated capability of inline electron holography provides a technical breakthrough for future strain engineering of piezoelectric optoelectronic devices.