Pseudomorphic growth of thick Al0.6Ga0.4N epilayers on AlN substrates
Abstract
We report on the absence of strain relaxation mechanism in Al0.6Ga0.4N epilayers grown on (0001) AlN substrates for thickness as large as 3.5 μm, three-orders of magnitude beyond the Matthews–Blakeslee critical thickness for the formation of misfit dislocations (MDs). A steady-state compressive stress of 3–4 GPa was observed throughout the AlGaN growth leading to a large lattice bow (a radius of curvature of 0.5 m−1) for the thickest sample. Despite the large lattice mismatch-induced strain energy, the epilayers exhibited a smooth and crack-free surface morphology. These results point to the presence of a large barrier for nucleation of MDs in Al-rich AlGaN epilayers. Compositionally graded AlGaN layers were investigated as potential strain relief layers by the intentional introduction of MDs. While the graded layers abetted MD formation, the inadequate length of these MDs correlated with insignificant strain relaxation. This study emphasizes the importance of developing strain management strategies for the implementation of the single-crystal AlN substrate platform for III-nitride deep-UV optoelectronics and power electronics.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 16, 2022
- Source ID
- 10.1063/5.0092937
Entities
People
- J. Houston Dycus
- James Tweedie
- Ramón Collazo
- Ronny Kirste
- Seiji Mita
- Shashwat Rathkanthiwar
- Zlatko Sitar
Organizations
- National Science Foundation
- North Carolina State University
- United States Army Research Laboratory