Epitaxial growth of 2.5-μm quaternary AlInGaN for n-cladding layer in GaN-based green laser diodes

The ridge morphology, which is related to random atomic step meandering, appears in thick AlInGaN films grown by metal organic chemical vapor deposition on both GaN templates and free-standing GaN substrates; this can be primarily attributed to the in-plane compressive strain in the thick layer. Therefore, a 2.5-μm Al0.08In0.0123GaN film with a slightly tensive strain was grown, with a regular and smooth step-flow morphology; the root mean square deviation of the film (with a size of 5 μm × 5 μm) was 0.56 nm.