Structure of V-defects in long wavelength GaN-based light emitting diodes

TitleStructure of V-defects in long wavelength GaN-based light emitting diodes
Publication TypeJournal Article
Year of Publication2023
AuthorsWu, F., J. Ewing, C. Lynsky, M. Iza, S. Nakamura, S. P. DenBaars, and J. S. Speck
JournalJournal of Applied Physics
Volume133
Date Published01
ISSN0021-8979
Abstract

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.

URLhttps://doi.org/10.1063/5.0135278
DOI10.1063/5.0135278