Investigation of (In, Ga)N/GaN Quantum Structure for Nitride Lasers
Abstract
Report developed under contract FA8718-08-C-0035. This is the final report for a project to experimentally and theoretically investigate (In,Ga)N/GaN quantum structures for applications in light-emitting devices. The nitride films were grown by molecular beam epitaxy. Their structural properties were characterized by rocking curve x-rays, and their optical quality was assessed by photoluminescence spectroscopy. The main finding is that nitride films grown directly on sapphire substrates were inferior to those grown on template substrates (which are thick bulk-like GaN or AlN layers on sapphire for growth initiation). The lattice constant of GaN cannot be matched to that of most ternary or quaternary films grown on it; compared to sapphire, however, with a mismatch of ~13.5% from GaN, GaN templates are a better alternative substrate. Furthermore, our theoretical analysis suggests that an even better alternative template substrate should be comprised of ternary nitride layers such as In Ga N x 1-x or Al Ga N. x 1-x unlike sapphire substrates or GaN templates, the lattice constants of the ternaries can be adjusted via their compositions to closely match the average lattice constant of the device layers to be grown on them. This minimizes lattice-mismatch induced strain which has a significant impact on the electronic band structure and on key optical properties of films intended for photonic devices.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2012
- Accession Number
- ADA557241
Entities
People
- E. Towe
Organizations
- Carnegie Mellon University