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7 III-Nitride LED Quantum Efficiency Improvement Technology
Fig. 7.11 Low temperature buffer layer grown on a planar substrate and a patterned substrate
before and after annealing. a and b are the shape of the buffer layer before annealing; c and d are
the morphology after annealing
longitudinal growth rate of gallium nitride is much larger than that of the lateral direction. Growing the 3D layer until the thickness is greater than or equal to the height of
the substrate pattern. At this stage, the real-time anti-reflectivity approaching 0. The
growth conditions are adjusted again such that the vertical growth rate of gallium
nitride is less than the lateral growth rate. This will lead to the 2D growth mode
until the epitaxial gallium nitride completely covers the substrate pattern and form
a flat surface as shown in Fig. 7.12. During the 3D growth process, the longitudinal
growth rate is enhanced. When the thickness can be compared with the height of the
substrate pattern, the 3D GaN layer encloses the pattern of the patterned substrate.
During the 2D growth process, GaN epitaxy rapidly grow along the inclined side
surface, which results in the bending of penetrating dislocation, thereby reducing the
dislocation defects in GaN epitaxial film.
Figure 7.13 is TEM image of epitaxy LED structure adopted 3D-2D growth
mode. Penetrating dislocations (region 1) turn toward the direction of the pattern,
where a small amount of penetration dislocations (region 2) still extend upward.
7 III-Nitride LED Quantum Efficiency Improvement Technology
Fig. 7.11 Low temperature buffer layer grown on a planar substrate and a patterned substrate
before and after annealing. a and b are the shape of the buffer layer before annealing; c and d are
the morphology after annealing
longitudinal growth rate of gallium nitride is much larger than that of the lateral direction. Growing the 3D layer until the thickness is greater than or equal to the height of
the substrate pattern. At this stage, the real-time anti-reflectivity approaching 0. The
growth conditions are adjusted again such that the vertical growth rate of gallium
nitride is less than the lateral growth rate. This will lead to the 2D growth mode
until the epitaxial gallium nitride completely covers the substrate pattern and form
a flat surface as shown in Fig. 7.12. During the 3D growth process, the longitudinal
growth rate is enhanced. When the thickness can be compared with the height of the
substrate pattern, the 3D GaN layer encloses the pattern of the patterned substrate.
During the 2D growth process, GaN epitaxy rapidly grow along the inclined side
surface, which results in the bending of penetrating dislocation, thereby reducing the
dislocation defects in GaN epitaxial film.
Figure 7.13 is TEM image of epitaxy LED structure adopted 3D-2D growth
mode. Penetrating dislocations (region 1) turn toward the direction of the pattern,
where a small amount of penetration dislocations (region 2) still extend upward.