发光二极管
材料科学
透射电子显微镜
光电子学
蓝宝石
超晶格
位错
Burgers向量
宽禁带半导体
量子阱
扫描透射电子显微镜
量子效率
散射
晶体缺陷
堆积
空位缺陷
二极管
结晶学
光学
纳米技术
物理
化学
激光器
核磁共振
复合材料
作者
Feng Wu,Jacob Ewing,Cheyenne Lynsky,Michael Iza,Shuji Nakamura,Steven P. DenBaars,James S. Speck
摘要
The V-defect is a naturally occurring inverted hexagonal pyramid structure that has been studied in GaN and InGaN growth since the 1990s. Strategic use of V-defects in pre-quantum well superlattices or equivalent preparation layers has enabled record breaking efficiencies for green, yellow, and red InGaN light emitting diodes (LEDs) utilizing lateral injection of holes through the semi-polar sidewalls of the V-defects. In this article, we use advanced characterization techniques such as scattering contrast transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy, x-ray fluorescence maps, and atom probe tomography to study the active region compositions, V-defect formation, and V-defect structure in green and red LEDs grown on (0001) patterned sapphire and (111) Si substrates. We identify two distinct types of V-defects. The “large” V-defects are those that form in the pre-well superlattice and promote hole injection, usually nucleating on mixed (Burgers vector b=±a±c) character threading dislocations. In addition, “small” V-defects often form in the multi-quantum well region and are believed to be deleterious to high-efficiency LEDs by providing non-radiative pathways. The small V-defects are often associated with basal plane stacking faults or stacking fault boxes. Furthermore, we show through scattering contrast transmission electron microscopy that during V-defect filling, the threading dislocation, which runs up the center of the V-defect, will “bend” onto one of the six {101¯1} semi-polar planes. This result is essential to understanding non-radiative recombination in V-defect engineered LEDs.
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