  High quality semipolar and nonpolar GaN is crucial in achieving
high-performance GaN-based optoelectronic devices, yet it has been very
challenging to achieve large-area wafers that are free of basal-plane stacking
faults (BSFs). In this work, we report an approach to prepare large-area,
stacking-fault-free (SF-free) semipolar GaN on (4-inch) sapphire substrates. A
root cause of the formation of BSFs is the emergence of N-polar (000-1) facets
during semipolar and non-polar heteroepitaxy. Invoking the concept of kinetic
Wulff plot, we succeeded in suppressing the occurrence of N-polar GaN (000-1)
facets, and consequently in eliminating the stacking faults generated in
(000-1) basal-planes. The result was confirmed by transmission electron
microscopy, cathodoluminescence, and low-temperature photoluminescence
characterizations. Furthermore, InGaN light emitting diodes with promising
characteristics have been produced on the SF-free semipolar (20-21) GaN on
sapphire substrates. Our work opens up a new insight about the heteroepitaxial
growth of nonpolar/semipolar GaN and provides an approach of producing SF-free
nonpolar/semipolar GaN material over large-area wafers which will create new
opportunities in GaN optoelectronic and microelectronic research.
