RF Performance of Ultra-wide Band Gap HEMTs
55
the conducting channel, and asymmetrical device geometry led localized self-mixing
results into nanometer spatial sensitivity. Further quasistatic self-mixing model [46,
48] developed by taking account the localized THz fields and described the important features of THz response and non-uniform THz fields; hence, local self-mixing
are investigated by selectively depleting the 2DEG near the edges of the channel. The device used AlGaN HEMT as THz detectors [48] by self-mixing, used
In 0.17 Al 0.83 N(24 nm)/GaN heterostructure with detector details: gate length of 2 μm
integrated with an asymmetric antenna, two patch antennas having gap of 3 μm
next to the gate, and the ohmic contacts (source and drain) kept close to the patch
antenna. An MSM-2DEG varactor [49] based on AlGaN/GaN HEMT was proposed
for THz multiplication, and most recently—bow-tie TeraFET [50] is demonstrated
with improved sensitivity by a factor of two in THz detection over other TeraFET
based on AlGaN/GaN HEMT. The device is an improved FETs furnished with inchip broadband bow-tie antenna (bow-tie TeraFET) for THz detection, and realized
a AlGaN/GaN HEMTs with 100 nm GaN MMIIC process, with a separation of d =
12 nm between gate and channel (width = 3 μm), gate length L g = 100 nm and two
300 nm wide access regions (ungated). AlGaN/GaN epitaxial layers were grown on
470 μm thick semi-insulating SiC substrate for THz frequencies. The THz radiation
was coupled through this transparent substrate. The THz detector used a broadband
antenna (bow-tie-type) which was fabricated using gold material of thickness 650nm. The 60 μm first wing antenna was designed with an wide angle of 60° to receive
the optimum radiated power. The second wing of the antenna is observed as MIM
capacitor and is realized as the capacitance two source and gate contacts separated
with a dielectric layer of SiNx 200-nm-thick (not shown in figure). Schematic of
cross-section of both versions of THz detector (TeraFET) is shown in Fig. 4.
Recent progress of device scaling technologies in GaN HEMTs paved the way
for many desirable characteristics: high frequency, low resistance, high-blocking
voltage, and low-noise, to name a few. These new features offer many practical
advantages in RF MMICs: high-efficiency switched-mode PAs, PA MMICs operation
in G-band and beyond, LNAs with low dc power dissipation, and robust low-loss
High resistivity Si (111)
S
D
Antenna
Antenna
G
InAlN
GaN
V ds
V ds
V gs
I pc + I ds
2DEG
V gs
(a)
(b)
Fig. 4 Cross section of the device schematic a GaN HEMT detector, b AlGaN/GaN TeraFET
55
the conducting channel, and asymmetrical device geometry led localized self-mixing
results into nanometer spatial sensitivity. Further quasistatic self-mixing model [46,
48] developed by taking account the localized THz fields and described the important features of THz response and non-uniform THz fields; hence, local self-mixing
are investigated by selectively depleting the 2DEG near the edges of the channel. The device used AlGaN HEMT as THz detectors [48] by self-mixing, used
In 0.17 Al 0.83 N(24 nm)/GaN heterostructure with detector details: gate length of 2 μm
integrated with an asymmetric antenna, two patch antennas having gap of 3 μm
next to the gate, and the ohmic contacts (source and drain) kept close to the patch
antenna. An MSM-2DEG varactor [49] based on AlGaN/GaN HEMT was proposed
for THz multiplication, and most recently—bow-tie TeraFET [50] is demonstrated
with improved sensitivity by a factor of two in THz detection over other TeraFET
based on AlGaN/GaN HEMT. The device is an improved FETs furnished with inchip broadband bow-tie antenna (bow-tie TeraFET) for THz detection, and realized
a AlGaN/GaN HEMTs with 100 nm GaN MMIIC process, with a separation of d =
12 nm between gate and channel (width = 3 μm), gate length L g = 100 nm and two
300 nm wide access regions (ungated). AlGaN/GaN epitaxial layers were grown on
470 μm thick semi-insulating SiC substrate for THz frequencies. The THz radiation
was coupled through this transparent substrate. The THz detector used a broadband
antenna (bow-tie-type) which was fabricated using gold material of thickness 650nm. The 60 μm first wing antenna was designed with an wide angle of 60° to receive
the optimum radiated power. The second wing of the antenna is observed as MIM
capacitor and is realized as the capacitance two source and gate contacts separated
with a dielectric layer of SiNx 200-nm-thick (not shown in figure). Schematic of
cross-section of both versions of THz detector (TeraFET) is shown in Fig. 4.
Recent progress of device scaling technologies in GaN HEMTs paved the way
for many desirable characteristics: high frequency, low resistance, high-blocking
voltage, and low-noise, to name a few. These new features offer many practical
advantages in RF MMICs: high-efficiency switched-mode PAs, PA MMICs operation
in G-band and beyond, LNAs with low dc power dissipation, and robust low-loss
High resistivity Si (111)
S
D
Antenna
Antenna
G
InAlN
GaN
V ds
V ds
V gs
I pc + I ds
2DEG
V gs
(a)
(b)
Fig. 4 Cross section of the device schematic a GaN HEMT detector, b AlGaN/GaN TeraFET