In situ wafer curvature measurement and strain control of AlInN/GaN distributed Bragg reflectors

We measured in situ wafer curvature evolutions of 25-pair AlInN/GaN DBRs on sapphire substrates and found that strains in the DBRs were gradually increased in a compressive direction as the epitaxial growth progressed. The increase of the strain was originated in the AlInN layers of the DBRs, suggesting a possibility that the InN mole fraction was increased with 0.03%–0.05%/pair. In order to compensate the increase of the strain in the AlInN layers, we grew the DBR by gradually increasing AlInN growth temperatures with 1°C/5 pairs, resulting in narrower satellite peaks of an X-ray diffraction pattern.