 A joint research team from the
University of Houston, Applied Optoelectronics
Inc. (AOI) and Cornell University has won an
intense race to develop a better way to build
lasers and other optoelectronic devices.
Just as the development of structural
steel revolutionized the construction industry,
this new technique dramatically expands the field
of epitaxy, the process used to manufacture high
performance semiconductor devices such as lasers,
optical detectors, and microwave device and
circuits. Dubbed the "compliant universal
substrate, 11
Dr. Chau-Hong Kuo of the Space Vacuum
Epitaxy Center (SVEC), the NASA Commercial Space
Center at UH, unveiled this new technique for
creating epitaxial thin film devices last week,
at the North American Molecular Beam Epitaxy
Conference in Pennsylvania.
"This technique will allow |
us to create lasers and optoelectronic
devices with better performance and lower costs
by relieving a lot of the materials constraints '
" said Steven Pei, associate director for
research at SVEC and professor of electrical
engineering.
The compliant universal substrate
concept was first proposed by scientists at
Cornell University in 1 996. Since then, research
groups around the world have raced to produce the
first device on the compliant substrate.
"AOI initiated this research under a grant
from the National Science Foundation's Small
crystalline structure must match the material
being placed on top. It's like trying to align
the grids on two pieces of graph paperthe grids
must match. Currently, only a few substrate
materials are available, fewer still are
affordable. Thus, materials requiring substrates
with different "grid sizes" can not be
used, greatly limiting researchers' options. |
The "compliant universal
substrate" is like a grid Epitaxy is a
technique for growing single crystal materials on
a base or substrate with atomic precision. A
combination of layers might produce a laser,
while another combination produces a high
efficiency solar cell. However, traditional
epitaxy faces one substantial hurdle: the
substrate's printed on a piece of rubber loosely
bonded to a conventional substrate. It expands or
contracts to match the grid of the epitaxy thin
film grown on top of it. By eliminating
concerns about matching the grids on the
underlying conventional substrate, the
universally compliant substrate dramatically
increases the choices of epitaxy thin films /
substrate combinations for optoelectronic
applications and may even lead to less expensive
base substrate materials. Researchers from SVEC
and AOI demonstrated the viability of the
technique by building a |
mid-infrared laser on the newcompliant
universal substrate bonded to an otherwise
incompatible substrate. The new structure
significantly improved the laser's cooling,
allowing it to produce more power. The NSF, Air
Force and Ballistic Missile Defense Organization
are currently funding the research at SVEC and
AOI to develop semiconductor midinfrared lasers
for environmental monitoring and jamming of
heat-seeking missilesAlthough applicable to all epitaxy
thin films, researchers expect this new technique
will be most useful for developing lasers and
other optoelectronic devices. For example, the
development of blue and ultraviolet lasers has
been hindered by the lack of an appropriate
substrate. With the compliant universal
substrate, researchers are one step closer to
producing blue lasers for color display and
high-density optical storage applications. |
