(gallium nitride) is a typical third generation materials of wide band gap
semiconductors in Material field. Compared with formal semiconductor materials,
GaN (gallium nitride) has a higher frequency, higher power, and higher density
for making integrated electronics. What’s more, the strong radiation resistance
ability for GaN (gallium nitride) could also make great contributions in
microwave power devices filed.
Properties for GaN
GaN (Gallium nitride) is very hard and stable chemical compound and it’s
melting point is about 2000K. Generally, the atomic structure for GaN (gallium
nitride) is closed-packed hexagonal structure and that results in relatively
low symmetry of lattice and strong piezoelectricity and ferroelectricity.
GaN (Gallium nitride) is regard as wide band gap semiconductor. The band
gap is 3.4 eV and thermal conductivity is 1.3 W/cm*K. This two factors lead to
the GaN (Gallium nitride) has a high working temperature and breakdown voltage
and a strong ability of radiation resistance. The bottom of conduction band of
GaN is at ? position which makes a huge energy difference with other with other
valley to resist the scattering between different valleys. As a result, GaN has
a very high saturated drift velocity of electrons.
Generally, wide-band gap semiconductors materials have band gaps in the
range of 2-4 eV, whereas typical semiconductors have band gaps in the range of
1-1.5 eV. Higher energy of band gap makes it suitable for working in a high
temperature. Wide band gap semiconductors are associated with a high voltage.
This is due to a large electric filed to generate carries through impact
However, GaN also has its
shortcomings. Because of it structure of energy bond, the electron mobility is
relatively low while the charge carriers have a high valuable mass.
Preparation for GaN
preparation of GaN (gallium nitride) includes four main steps: metalorganic
chemical vapor deposition, hydride vapor phase epitaxy, separation and second
MOCVD step, ultra-pure gases are transferred into a reactor and finally result
in a deposition of a very thin layer of atoms onto a semiconductor wafer. For
instance, Pin can be grown in a heated substrate by trimethylindium and
molecular decomposition happens in the absence of oxygen. As to the equipment,
the reaction chamber is the most important part which is composed by several
units such as reactor walls, liner, susceptor, gas injection units and
temperature control units.
temperature should be carefully noticed when we heat the substrate. One is
around 823K and another is around 1273K. In the low
temperature condition, there will be a buffer layer growing firstly. However,
in the high temperature, GaN (gallium nitrate) will grow directly. So the temperature should be controlled.
The HVPE makes the GaN (gallium nitrate) grow continually. The hydrogen
chloride is reacted at a certain temperature while the group (III) metal producing
gaseous metal chlorides and then it will react with ammonia to produce group (III)
As to the separation part, the technique of laser lift-off is better than
natural separation which uses high power pulsed laser directly to the surface.
the typical application for GaN (gallium nitride) is power devices. Compared
GaN (gallium nitride) with other materials, it has relatively small volume and
high efficiency to transport. Nowadays, as the popularization of 4G cell site
and wireless power, the potential market could be expected too.
from the strong ability for GaN (gallium nitride) to transport information, the
high luminous efficiency of GaN (gallium nitride) also could be applied to the
LED. For instance, many companies have put their eye on the research and
exploitation on GaN (gallium nitride) materials, like Samsung, Mitsubishi etc.
to the graph mentioned on the slides, it can easily show us the promising
future of GaN (gallium nitride), the statistics also show that the total value
in US in 2015 has arrived at 298 million Dollars, and many of the cost is
concentrated on wireless infrastructure.