Project Title:

Blue Indium-Gallium-Nitride LEDs for Plant Growth and Development

94-1	12.04	7000		

Blue Indium-Gallium-Nitride LEDs for Plant Growth and Development 

Abstract:

The proposed Phase I research program will initiate a demonstration 
of new high-brightness, blue-light-emitting diodes (LED) required 
for effective plant growth on the Space Shuttle. Without a source 
of blue photons, dicotyledonous plants develop excessive hypocotyl 
elongation when illuminated solely by the red LED lamps now 
available as a photosynthetic radiation source for NASA. Films of 
indium-gallium-nitride (InGaN), the basis for bright-blue LEDs, 
will be grown by plasma-assisted metalorganic chemical vapor 
deposition (PA-MOCVD) and doped p-type by ion implantation. Use of 
a plasma source of nitrogen eliminates the harmful effects of 
hydrogen on inhibiting p-type doping that always accompany growth 
of nitrides from ammonia; functional LEDs require a pn junction and 
thus p-type doping is a critical materials issue. Introducing 
magnesium p-type dopants by implantation further avoids 
inadvertently incorporating hydrogen from organic-Mg doping 
sources. 
Phase I will establish conditions for materials deposition and p-
type doping of InGaN, including an annealing schedule; preliminary 
assessment of the role of blue GaN LEDs on plant growth will be 
carried out by the Botany Department of the University of 
Wisconsin. Optimization of blue LED performance will be undertaken 
in Phase II. Here we shall extend the work to create a tandem 
red/blue InN/GaN LED which can emit all of the photons needed by 
plants raised in space. Grown as a large area film on a totally 
transparent substrate, this light-source approach will avoid the 
costly assembly of tiny LED dice. 

Because alloys of the III-V nitrides span the entire visible 
spectrum, they can be used in many commercial applications 
including full color displays for HDTV; indicator lights and alpha-
numeric displays; free space communications (including optical 
interconnects in computers), and high density optical data storage, 
including advanced bar code readers. 

plant growth, blue light-emitting diodes, indium-gallium-nitride, 
plasma-assisted MOCVD, ion implantation, tandem red/blue LED 

Spire Corporation        
One Patriots Park                          
Bedford, MA 01730-2396