Optical and crystal improvements of semipolar (11-22) GaN/m-sapphire by in-situ thermal etching process

• Optical/crystal qualities of semipolar (11-22) GaN were improved by 3-step growth.
• The 3-step growth consisted of seed GaN growth, I-STEP and lateral growth step.
• XRC FWHMs of semipolar (11-22) GaN were decreased by 3-step growth.
• PL intensity of semipolar (11-22) GaN was improved by 3-step growth.

We investigated the optical and crystal qualities of semipolar (11-22) GaN grown on m-plane sapphire using three-step growth technique which consisted of seed GaN growth, in-situ thermal etching process (I-STEP), and lateral growth step. By introducing three-step growth, we achieved high optical and crystal qualities of semipolar (11-22) GaN films compared with those grown by conventional one-step growth. In particular, as the positions of I-STEP were decreased from 1.0 to 0.25 μm toward sapphire substrate, the full width at half maximum of the X-ray rocking curve was effectively decreased from 1083 to 828 arcsec, respectively. Furthermore, photoluminescence results showed that the bandedge emission intensity of semipolar (11-22) GaN with I-STEP was 56% higher than that with conventional growth technique. Based on these results, we suggested that the three-step growth would be effective to improve the crystal and optical qualities of semipolar (11-22) GaN/m-sapphire.