Stacking faults and interface roughening in semipolar $(202¯1¯)$ single InGaN quantum wells for long wavelength emission

The microstructure of InGaN single quantum wells (QWs) grown in semipolar $(202¯1¯)$ orientation on GaN substrates was studied by transmission electron microscopy. Stress relaxation in the lattice mismatch In_xGa_1−xN layer was realized by forming partial misfit dislocations associated with basal plane stacking faults (BPSFs). For given composition x = 0.24, BPSFs formation was observed when the QW thickness exceeded 4 nm. The high density of partial threading dislocations that bound the BPSFs is detrimental to light-emitting device performance. Interface roughening (faceting) was observed for both upper and lower QW interfaces (more pronounced for upper interface) and was found to increase with the thickness of the QW. BPSFs had a tendency to nucleate at roughened interface valleys.