Microstructural characteristization of InGaN/GaN epitaxial Layers with Pt nanoclusters grown by using MOCVD on c-plane sapphire substrates

Transmission electron microscopy (TEM) was used to survey the microstructures of InGaN/GaN epitaxial layers deposited on c-plane sapphire substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. Pt nanoclusters were deposited at the InGaN/GaN epitaxial layer/sapphire substrate (sample A) interface and under the multi-quantum-well (MQW) layers (sample B), aiming at understanding the effect of the Pt nanoclusters on the microstructural characteristics of the epitaxial layers. Experimental results showed that the growth of the epitaxial layer in sample A was much better than that in sample B. The dislocation densities were measured as ~10 ⁷ cm ^-2 and ~10 ⁸ cm ^-2 in sample A and sample B, respectively. The lower dislocation density in sample A was due to threading dislocations (TDs) being stopped by the nanoclusters at the interface. For MQWs in light-emitting layers, the interfaces between the InGaN and the GaN barriers in sample A were very obvious and straight whereas those in sample B were not.