High Efficiency Light Emission Through Carrier Localization in AlGaN Alloys and Active Regions: Toward Viable Ultraviolet Light Sources for the Objective Force Warrior
Abstract
AlGaN samples growth by plasma-assisted molecular beam epitaxy on sapphire (0001) substrates, with 20-50% Al content and without the use of indium, show intense room temperature photoluminescence that is significantly red-shifted. 200-400 meV, from band edge. This intense emission is characterized by a long room temperature lifetime (^300-400 ps) comparable to that seen in low defect density (^10(exp 8)/sq cm) GaN. Room temperature monochromatic scanning cathodoluminescence images at the red-shifted peak reveal spatially non-uniform emission similar to that observed in In(Al)GaN alloys and attributed to compositional inhomogeneity. These observations suggest that spatial localization enhances the luminescence efficiency despite the high defect density (>10(exp 10)/sq cm) of the films by inhibiting movement of carriers to nonradiative sites. Significant enhancement of this phenomenon has been obtained in a DH LED structure grown on a lower defect density AIGaN template, with PL lifetime increased by nearly a factor of two, corresponding to a defect density in the mid-10(exp 7)/sq cm) range, and an internal quantum efficiency of ^30%. These results open the possibility of viable, low cost UV LEDs for bioagent detection and covert communication systems that provide protection and information at the individual soldier level and aid the development of survivability, lethality, and deployability of the Objective Force.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2004
- Accession Number
- ADA433666
Entities
People
- A. V. Sampath
- A. Y. Nikiforov
- C. J. Collins
- G. A. Garrett
- G. S. Cargill
- Haoting Shen
- M. Wraback
- Volkmar Dierolf
- Wendy L. Sarney
Organizations
- United States Army Research Laboratory