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Correlative High‐Resolution Mapping of Strain and Charge Density in a Strained Piezoelectric Multilayer
Author(s) -
Song Kyung,
Koch Christoph T.,
Lee Ja Kyung,
Kim Dong Yeong,
Kim Jong Kyu,
Parvizi Amin,
Jung Woo Young,
Park Chan Gyung,
Jeong Hyeok Jae,
Kim Hyoung Seop,
Cao Ye,
Yang Tiannan,
Chen LongQing,
Oh Sang Ho
Publication year - 2015
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201400281
Subject(s) - piezoelectricity , materials science , optoelectronics , electron holography , polarization (electrochemistry) , semiconductor , strain engineering , electron , strain (injury) , diode , quantum well , optics , nanotechnology , silicon , composite material , physics , medicine , laser , chemistry , quantum mechanics , transmission electron microscopy
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 In 0.15 Ga 0.85 N 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 In 0.15 Ga 0.85 N quantum well. The demonstrated capability of inline electron holography provides a technical breakthrough for future strain engineering of piezoelectric optoelectronic devices.