Low-Cost Substrates for High Performance Nanorod Array LEDs
Investigating Organization
Purdue University
Principal Investigator(s)
Timothy D. Sands
Subcontractor
None
Funding Source
Building Technologies Program/NETL
Award
DOE Share: $899,948; Contractor Share: $225,195
Contract Period
05/01/06 - 04/30/09
The primary emphasis is aimed at improving the internal quantum efficiency (IQE) of GaN-based LEDs has been on reducing the threading dislocation density, these approaches including epitaxial lateral overgrowth, bulk GaN substrates and bulk SiC substrates - inevitably increase the materials or manufacturing costs markedly. This project is designed to exploit the relief of lattice mismatch strain and the expulsion of dislocations that are characteristic of nanoheteroepitaxy in the growth of heteroepitaxial device structures on nanoscale substrates to expand the spectral range of efficient GaN-based LEDs to include the entire visible spectrum, thereby eliminating the efficiency losses associated with phosphor down-conversion. The investigators have demonstrated the fabrication of uniform arrays of GaN nanorods using a low-cost process that does not involve foreign catalysts or direct-write nanolithography.
Nanorod array geometries that effectively exclude dislocations have been determined by computational methods, and verified experimentally. Nanorod LEDs that emit in the yellow-orange portion of the spectrum have been demonstrated. Furthermore, the nanorod process has been transferred to a novel metallized silicon substrate, replacing the sapphire or SiC substrate with a scalable alternative.