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Minho
Intro
Good morning. I’m Minho kim, Ph.D. student, from tech university of
Korea. Today I’m going to talk about AlGaN/GaN/AlN double-hetero
structure with high-quality AlN buffer grown on SiC substrate.
This is an outline of my presentation. Introduction, results &
Discussion, and summary.
GaN HEMT is a very promising material for power and RF devices
compared to the Si and GaAs due to their high breakdown voltage, low
Ron and fmax. So, it can be used with High power and high frequency
devices. Recently, GaN HEMT devices have been widely used in this
application below.
This is a typical GaN based HEMT epi structure. HEMTs device need
these characteristics like this. And the buffer is the most important
thing. The buffer layer needs both high quality and semi-insulating
properties together. Some dopants are used to make semi-insulating
properties, such as carbon and iron. And these doping gases become
defects such as point defects or dislocations. These defects act as a
trap center in the buffer layer and reduce breakdown voltage and
causes current collapse. Furthermore, some group reported the AlGaN
buffer or back-barrier using band engineering by increasing the Al
mole fraction. However, thermal conductivity was rapidly decreased.
That is why AlN buffer is a good approach for the previous issues.
Looking at a figure and table, AlN has a higher critical electric field and
a higher figure of merit than any other material. Furthermore, hetero
growth is possible on Si, sapphire, and SiC substrate. So, if we replace
the buffer to the AlN, we can expect excellent properties. Due to these
advantages, several groups have reported studies using AlN as a
buffer. These figures show the results of previous studies based on the
AlN buffer, showing high reliability and potential for RF devices. This
result shows a breakdown voltage value of 600V at a 40nm gate and
excellent dispersion. It also shows a very good breakdown voltage
characteristics in thin GaN channel layer and in the case of the AlN
barrier, this research shows a high 2DEG concentration and excellent
fT despite of low electron mobility.
