1 research outputs found
Evolution of the <i>m</i>‑Plane Quantum Well Morphology and Composition within a GaN/InGaN Core–Shell Structure
GaN/InGaN
core–shell nanorods are promising for optoelectronic applications
due to the absence of polarization-related electric fields on the
sidewalls, a lower defect density, a larger emission volume, and strain
relaxation at the free surfaces. The core–shell geometry allows
the growth of thicker InGaN shell layers, which would improve the
efficiency of light emitting diodes. However, the growth mode of such
layers by metal organic vapor phase epitaxy is poorly understood.
Through a combination of nanofabrication, epitaxial growth, and detailed
characterization, this work reveals an evolution in the growth mode
of InGaN epitaxial shells, from a two-dimensional (2D) growth mode
to three-dimensional (3D) striated growth without additional line
defect formation with increasing layer thickness. Measurements of
the indium distribution show fluctuations along the <10–10>
directions, with low and high indium composition associated with the
2D and 3D growth modes, respectively. Atomic steps at the GaN/InGaN
core–shell interface were observed to occur with a similar
frequency as quasi-periodic indium fluctuations along [0001] observed
within the 2D layer, to provide evidence that the resulting local
strain relief at the steps acts as the trigger for a change of growth
mode by elastic relaxation. This study demonstrates that misfit dislocation
generation during the growth of wider InGaN shell layers can be avoided
by using pre-etched GaN nanorods. Significantly, this enables the
growth of absorption-based devices and light-emitting diodes with
emissive layers wide enough to mitigate efficiency droop