Introduction is composed by reactor walls, liner, susceptor,

Introduction

 GaN
(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.

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Properties for GaN (gallium nitride)

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 mechanism.

   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 (gallium nitride)

The
preparation of GaN (gallium nitride) includes four main steps: metalorganic
chemical vapor deposition, hydride vapor phase epitaxy, separation and second
growth.

In
the 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
phosphine.

The
precursor molecular decomposition happens in the absence of oxygen. As to the
equipment, the reaction chamber is the main body that is composed by reactor
walls, liner, susceptor, gas injection units and temperature control units.

Besides,
two temperature should be paid attention 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 hydride vapor
phase epitaxy (HVPE) makes the GaN (gallium nitrate) grow continually. The hydrogen
chloride is reacted at elevated temperature while the group (III) metal producing
gaseous metal chlorides and then it will react with ammonia to produce group (III)
metal nitride.

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 energy of light is
between Esubstrate and EGaN.

Applications

 
One of 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.

 Besides from the strong ability for GaN
(gallium nitride) to transport information, the high color rendeing index and
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.

 According 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.