JED - June 2017 - 35

TECHNOLOGY SURVEY
A SAMPLING OF GaN TRANSISTORS
By Ollie Holt

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BJTs just refer to the typical bipolar transistor junction of the original npn or pnp type transistors.
MOSFETS refers to metal oxide semiconductor field
effect transistors. They differ from BJT transistors
because they have a gate separating two electrodes
that determines the conductivity of the device. Enhancement-mode MOSFETS just add an oxide field to
increase conductivity. HEMT is a semiconductor that
uses materials that have dissimilar band gaps.
Some companies just grow the wafers for other
companies to integrate into different applications,
while other companies both grow the wafers and
integrate them into components. This survey only
refers to component - individual transistors integrated into a circuit such as a switch or an amplifier.
The survey was sent out to companies who manufacture GaN power amplifier (PA) components that
can be used in defense electronics applications. In
the survey table, the first column shows the model
number for the GaN transistor, and the second column lists the operational frequency range of the
component. The next column provides the output
power and/or gain provided by the device. The fifth
column indicates the transistor's Power Aided Efficiency (PAE) (i.e., the output power (RF) minus the
input power (RF) divided by the DC power. The next
column shows the transistor's reliability. Note that
a transistor's ability to operate at high temperature
levels extends its reliability. However, the higher
operating temperature levels also pose a challenge,
because the heat generated by the device has to be
removed from the system. Different substrate materials can aid in removing heat from the transistor
components. Operating voltage (listed in the next
column) also separates GaN technology from other
low band gap transistors because it can operate with
much higher voltages. The next columns show the
operational temperature range and the packaging
type. Because this survey is relatively broad, multiple types of packaging were included from simple
die which could be used on a microwave assembly,
surface mount, or a complete monolithic microwave
integrated circuit (MMIC) assembly.
Next month's survey will cover radar warning
receiver (RWR) and electronic support measures
(ESM) systems.

The Journal of Electronic Defense | June 2017

T

his month, we are taking a look at
Gallium Nitride (GaN) transistors that
can be used in a variety of defense electronics applications, including radios,
EW systems, and radars. Semiconductors,
have the unique property that they are
neither conductors nor insulators. Insulators have a
wide energy gap between the valence and conduction bands making them unable to conduct electricity, while conductors have no gap allowing the easy
flow of electricity. Solid-state physics refers to this
energy gap as the band gap. This energy difference
between the valence and conduction bands is measured in electron volts (eV). Most transistors have a
band gap of about 1 eV, examples being Silicon (Si)
at 1.11 eV, Germanium (Ge) at 0.67 eV, while Gallium
Arsenide (GaAs) is at 1.43 eV and Gallium Nitride at
3.4 eV. Materials with band gaps greater than around
1.7 eV are typically referred to as wide band gap
materials.
Both GaN and GaAs are known as compound semiconductors. That's because they either have three
(III) valance electrons (Gallium) or five (V) valance
electrons (Arsenic or Nitrogen) resulting in being
called III-V Semiconductors. This unique covalent
bond of eight electrons results in high electron
mobility transistors (HEMTs), which can operate at
much higher frequencies than silicon transistors,
which have lower electron mobility.
NOVE
MB
This wide band gap results in properties that
E
R not inherent in materials with lower band gaps.
are
These properties include a higher breakdown field,
which allows them to operate at higher voltages and
higher electron saturation velocities, which translates into higher power densities. A high power density means more power can be produced in a smaller
semiconductor area. Also, smaller area means lower
capacitances resulting in higher operating frequencies. GaN also has very good thermal characteristics
providing reliable operation at higher temperatures
and longer life.
GaN and GaAs transistors can be implemented in
different technologies. Some technology types are
more applicable to certain uses than others. Examples are; bipolar junction transistors (BJT), enhancement mode MOSFETS, HEMTs and many other types.

35



JED - June 2017

Table of Contents for the Digital Edition of JED - June 2017

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
DIRCM Past & Present
Technology Survey: GaN Transistors
EW 101
Report from the 42nd Annual Collaborative EW Symposium
AOC News
2017 AOC International Election Guide
JED Quick Look
Index of Advertisers
JED - June 2017 - intro
JED - June 2017 - cover1
JED - June 2017 - cover2
JED - June 2017 - 3
JED - June 2017 - 4
JED - June 2017 - 5
JED - June 2017 - The View From Here
JED - June 2017 - 7
JED - June 2017 - Conferences Calendar
JED - June 2017 - 9
JED - June 2017 - Courses Calendar
JED - June 2017 - 11
JED - June 2017 - From the President
JED - June 2017 - 13
JED - June 2017 - 14
JED - June 2017 - insert1
JED - June 2017 - insert2
JED - June 2017 - The Monitor
JED - June 2017 - 16
JED - June 2017 - 17
JED - June 2017 - 18
JED - June 2017 - 19
JED - June 2017 - 20
JED - June 2017 - 21
JED - June 2017 - World Report
JED - June 2017 - 23
JED - June 2017 - DIRCM Past & Present
JED - June 2017 - 25
JED - June 2017 - 26
JED - June 2017 - 27
JED - June 2017 - 28
JED - June 2017 - 29
JED - June 2017 - 30
JED - June 2017 - 31
JED - June 2017 - 32
JED - June 2017 - 33
JED - June 2017 - 34
JED - June 2017 - Technology Survey: GaN Transistors
JED - June 2017 - 36
JED - June 2017 - 37
JED - June 2017 - 38
JED - June 2017 - 39
JED - June 2017 - 40
JED - June 2017 - 41
JED - June 2017 - 42
JED - June 2017 - EW 101
JED - June 2017 - 44
JED - June 2017 - Report from the 42nd Annual Collaborative EW Symposium
JED - June 2017 - AOC News
JED - June 2017 - 47
JED - June 2017 - 2017 AOC International Election Guide
JED - June 2017 - 49
JED - June 2017 - 50
JED - June 2017 - 51
JED - June 2017 - 52
JED - June 2017 - 53
JED - June 2017 - 54
JED - June 2017 - 55
JED - June 2017 - JED Quick Look
JED - June 2017 - Index of Advertisers
JED - June 2017 - 58
JED - June 2017 - cover3
JED - June 2017 - cover4
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