Investigation of Microstructure and V-Defect Formation in InxGa1-xN/GaN MQW Grown Using Temperature-Gradient Metalorganic Chemical Vapor Deposition.

Temperature-gradient metalorganic chemical vapor deposition (MOCVD) was used to deposit In_xGa_1-xN/GaN multiple quantum well (MQW) structures with a concentration gradient of indium across the wafer. These MQW structures were deposited on low defect density (2 x 10⁸ cm^-2) GaN template layers for investigation of microstructural properties and V-defect (pinhole) formation. Room temperature (RT) photoluminescence (PL) and photomodulated transmission (PT)were used for optical characterization, which show a systematic decrease in emission energy for a decrease in growth temperature. Triple-axis x-ray diffraction (XRD), scanning electron microscopy, and cross-sectional transmission electron microscopy were used to obtain microstructural properties of different regions across the wafer. Results show that there is a decrease in crystal quality and an increase in V-defect formation with increasing indium concentration. A direct correlation was found between V-defect density and growth temperature due to increased strain and indium segregation for increasing indium concentration. [ABSTRACT FROM AUTHOR]