Stacking faults in quaternary In_xAl_yGa_1-x-yN layers

Quaternary In_0.12Al_0.29Ga_0.59N and In_0.10Al_0.02Ga_0.88N 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 In_0.10Ga_0.90N layers, SF density increases substantially in the In_0.10Al_0.02Ga_0.88N layer with only 2% additional Al. Z-contrast annular dark-field images showed that SFs are Al-rich in the In_0.12Al_0.29Ga_0.59N layer, but not in the In_0.10Al_0.02Ga_0.88N layer. Two reference Al_xGa_1-xN layers were grown using identical conditions except the carrier gases. Using H₂ carrier gas resulted in a ∼400 nm thick Al_0.45Ga_0.55N layer with no SFs, while using N₂ carrier gas resulted in a ∼250 nm thick Al_0.25Ga_0.75N 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.