Improvement of crystallinity and luminescence of GaN-based laser diode structure with suppressed curvature variation in active layers

Abstract

The influence of curvature variation on the crystallinity and luminescence of GaN-based blue laser diode (LD) structure is comprehensively investigated during the growth of InGaN/GaN active layers. Compared with InGaN/GaN multiple quantum well (MQWs) grown by the conventional 2-temperature deposition, curvature variation is successfully suppressed and a much gentler deformation from wells to barriers is obtained by employing same-temperature deposition method (STDM). With less curvature fluctuation, the V-pit density of InGaN/GaN MQWs grown on sapphire is effectively decreased from 4.5 × 108/cm2 to 2.8 × 108/cm2 with average root-mean-square roughness of 0.55 nm, while threading dislocation density of the GaN-based LD structures grown on FS-GaN is also reduced from 5.9 × 106/cm2 to 1.6 × 106/cm2. Additionally, an ~ 7 nm redshift in photoluminescence emission for LD structure is achieved, accompanied by a ~ 6 times higher emission intensity. A more uniform distribution of emission wavelength along the radial direction is observed and the full width at half maximum is also narrowed, indicating that the STDM is advantageous to effectively eliminate the negative influence of curvature variation and contribute to fabricating high-performance GaN-based light-emitting diodes and LDs.