Elimination of basal-plane stacking faults in semipolar/nonpolar GaN and light emitting diodes heteroepitaxially grown on sapphire substrates

Abstract

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.