Stacking faults in quaternary InxAlyGa1−x−yN layers

Quaternary In0.12Al0.29Ga0.59N and In0.10Al0.02Ga0.88N layers ∼200 nm thick were grown on (0 0 0 1) GaN/sapphire composites using metalorganic chemical vapor deposition. The layers were studied using transmission electron microscopy (TEM). TEM results indicate that the quaternary layers contain high-density stacking faults (SFs). Weak-beam dark-field analysis coupled with high-resolution electron microscopy reveal that SFs have zinc-blende structures bounded by Shockley partials. Compared with In0.10Ga0.90N layers, SF density increases substantially in the In0.10Al0.02Ga0.88N layer with only 2% additional Al. Z-contrast annular dark-field images showed that SFs are Al-rich in the In0.12Al0.29Ga0.59N layer, but not in the In0.10Al0.02Ga0.88N layer. Two reference AlxGa1−xN layers were grown using identical conditions except the carrier gases. Using H2 carrier gas resulted in a ∼400 nm thick Al0.45Ga0.55N layer with no SFs, while using N2 carrier gas resulted in a ∼250 nm thick Al0.25Ga0.75N layer with SFs. It is suggested that the low surface mobility of (CH3)2Al:NH2 species in the N2 environment led to SF formation in the quaternary layers.