Lead Performer: Lumileds – San Jose, CA
DOE Total Funding: $1,351,110
Project Term: October 1, 2017 – September 30, 2019
Funding Type: SSL R&D Funding Opportunity Announcement (FOA) (DE-FOA-0001613)
Project Objective
This project will improve the external quantum efficiency (EQE) of amber and red aluminum gallium indium phosphide (AlGaInP)-based LEDs by developing strain-engineered cladding layers to provide enhanced carrier confinement. The objective will be achieved by gaining a detailed understanding of the nature of defects associated with strained carrier confinement layers in state-of-the-art LED structures, and then optimizing the metal organic chemical vapor deposition (MOCVD) growth conditions to minimize material quality degradation due to these defects.
Project Impact
Poor radiative recombination efficiency in direct-emitting amber and red AlGaInP LEDs is a major barrier to achieving energy efficient color-mixed and color-tunable solid-state lighting. A higher Al composition in the active region, as required to reach amber and red wavelengths, reduces the amount of conduction band offset between the active layer and the cladding layer, causing overflow of the injected electrons into the cladding layer. In this project, strain-engineered cladding layers will be used to increase the conduction band offset between the cladding layer and the active layer to achieve increased radiative recombination in the LEDs. A critical success factor for this approach is a detailed understanding of the atomistic and electronic characteristics of defects arising in the strained AlGaInP layers. To this end, a combination of advanced characterization techniques will be used to probe deep-level defects and correlate them to growth conditions. Epitaxy designs and growth processes will be developed to implement optimized strained layers and realize the targeted gains in EQE for amber and red emission.
Contacts
DOE Technology Manager: James Brodrick, [email protected]
Lead Performer: Ted Chung, Lumileds