Structural and optical properties of InGaN/GaN multiple quantum wells grown on nano-air-bridged GaN template

Structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) grown on nano-air-bridged GaN template by metal organic chemical vapor deposition were investigated. The InGaN/GaN MQWs on nano-air-bridged GaN demonstrate much better surface morphology, revealing low defect density ∼4×10⁸ cm^-2 with step flow features measured by atomic force microscopy. The photoluminescence measurement shows one magnitude higher in intensity from less defective InGaN MQWs compared to that of the control InGaN MQWs. The improvement in photoluminescence of the InGaN MQWs is benefited from the reduction of threading dislocation density in the InGaN/GaN active layers and GaN template, revealed from cross-sectional transmission electron microscopy. High resolution x-ray diffraction analysis results show higher indium mole fraction in the MQWs when grown on nano-air-bridged GaN template, due to the strain relaxation in the nano-air-bridged GaN template. This higher indium incorporation is consistent with the redshift of the photoluminescence peak.