Abstract
With an annual volume of more than 5 millions units of 2" equivalent
substrates, GaN-based green, blue and white LED is the main eater of nitride
materials targeting a $3.5B market at devices level. Current split shows that
SiC substrates is accounting for ~10% of the total production, sapphire making
the balancing.
Sapphire market for LED is now tending toward equilibrium with 2/3 LED
manufactured on 2" and 1/3 on 3" substrates and a recent introduction of 4"
production announced by Japanese Showa Denko. Sapphire material market has
then just beaten the $150M barrier in 2006.
SiC is also entering in a 4" production stage at CREE but cannot be considered
as a real open market.
The substrate market playground can be seen as partially unstable because of
the rapid emergence of new substrates for GaN epitaxy. GaN-on-Silicon,
GaN-on-ZnO, GaN-on-Germanium, GaN-on-Glass, GaN-on-AlN and composite
substrates like GaN-on-diamond or Picogiga GaN-on-SopSiC are now pursuing the
same Rubicon: propose the best compromise between GaN quality, large diameter,
low bowing, high Tc, controlled TCE and of course, low cost. 6" is the main
target and is now available of-the-shelf from selected companies. That is
opening new doors to higher LED productivity toward the gigantic SSL general
illumination business.
In the RF business, GaN HEMT is now ready to challenge Si LDMOS and GaAs pHEMT
in the telecommunication base stations market (3G, 4G, WiMAX…). With
devices reaching Psat=174W @ 6GHz under 48V polarisation, the GaN technology
can be partially implemented among the 2 millions deployed mobile phone base
stations and coming next WiMAX infrastructures. A 10,000 x 4" epiwafers market
is forecasted in a very near future.
Gallium Nitride (GaN), as silicon carbide (SiC), is a wide bandgap material
allowing reaching high breakdown voltage. Thus road to power electronics
applications is wide open. However, GaN growth is based on an ethero epitaxy
process with often an AlN nucleation layer forcing the devices to be designed
laterally. Lateral devices are limited in term of breakdown voltage compared
to vertical ones and become rapidly bulky for high power density ranges.
This situation deals with a subtle balance between substrate diameter, power
density, chip size and device cost. In other terms, GaN power devices on
sapphire, silicon or composite substrates can compete with SiC from a cost
point of view using larger substrates (4") to compensate the bigger chip size
at a given power density.
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