RF Performance of Ultra-wide Band Gap HEMTs
59
temperature of Ga 2 O 3 HEMT on sapphire and Ga 2 O 3 remains around 200 °C limited
to P out ~2 W/mm; however Ga 2 O 3 with channel thickness of 1 μm and with no
substrate, can deliver P out ~7 W/mm. Furthermore, due to significant low electron
mobility in Ga 2 O 3 (~200 cm
2 V
−1 s
−1 ), Ga 2 O 3 HEMTs pose a dismal picture in
terms of efficiency and power dissipation on comparison of GaN HEMTs (electron
mobility ~2000 cm
2 V
−1 s
−1 ) vis-à-vis power switching applications; large periphery
of Ga 2 O 3 devices required to match GaN switching performance.
5 Conclusion
Ultra-wide bandgap materials: GaN-, Ga 2 O 3 -based HEMTs show good performance
metrics to achieve high output power density with large operating voltage and up
to THz frequency range; these devices can well serve the requirement of rapidly
expanding consumer applications: High-speed mobile Internet, hybrid and electric vehicle, efficient data centers, wireless charging, renewable energy systems, to
name a few. GaN-based HEMTs have achieved significant progresses relating to RF
applications in variety of areas: from material growth, device structure, processing
technology, MMIC and intersubband (ISB) technologies, to THz spectroscopy, and
imaging systems. GaN-based devices: HEMT successfully operated at ~600 GHz, for
THz detection, PAs MMIC achieved P out ~50 W/mm. Ga 2 O 3 having unique material
properties and large-size substrate availability (as compared to GaN), which improve
its cost/performance metric over GaN, and finds exclusive applications—high power
RF devices operating at low frequency—military-owned low-frequency high-voltage
application, and AC-to-DC conversion utilities. Ga 2 O 3 based HEMTs achieved CW
output power of 13.7 dBm at 800 MHz with PAE of 6.3%, while small signal cut-off
frequency of 3.3 GHz. Although very low electron mobility and poor thermal conductivity of β-Ga 2 O 3 restrict high power operation due to significant increase in channel
temperature led reduced electron mobility, although highly scaled devices having
ballistic transport may address the issue. It is concluded that GaN- and β-Ga 2 O 3
HEMTs can fully serve the entire RF power electronics application field based on
commercial and technical aspects to choose the perfect one for the right application.
Acknowledgements This publication is an outcome of the R&D work undertaken by the project
under the Visvesvaraya Ph.D. Scheme of Ministry of Electronics and Information Technology
(MeitY), Govt. of India, being implemented by Digital India Corporation. Acknowledgement also
goes to New Jersey Institute of Technology (NJIT), Newark, USA, for facilitating the visit of T. R.
Lenka for collaborative research work.
59
temperature of Ga 2 O 3 HEMT on sapphire and Ga 2 O 3 remains around 200 °C limited
to P out ~2 W/mm; however Ga 2 O 3 with channel thickness of 1 μm and with no
substrate, can deliver P out ~7 W/mm. Furthermore, due to significant low electron
mobility in Ga 2 O 3 (~200 cm
2 V
−1 s
−1 ), Ga 2 O 3 HEMTs pose a dismal picture in
terms of efficiency and power dissipation on comparison of GaN HEMTs (electron
mobility ~2000 cm
2 V
−1 s
−1 ) vis-à-vis power switching applications; large periphery
of Ga 2 O 3 devices required to match GaN switching performance.
5 Conclusion
Ultra-wide bandgap materials: GaN-, Ga 2 O 3 -based HEMTs show good performance
metrics to achieve high output power density with large operating voltage and up
to THz frequency range; these devices can well serve the requirement of rapidly
expanding consumer applications: High-speed mobile Internet, hybrid and electric vehicle, efficient data centers, wireless charging, renewable energy systems, to
name a few. GaN-based HEMTs have achieved significant progresses relating to RF
applications in variety of areas: from material growth, device structure, processing
technology, MMIC and intersubband (ISB) technologies, to THz spectroscopy, and
imaging systems. GaN-based devices: HEMT successfully operated at ~600 GHz, for
THz detection, PAs MMIC achieved P out ~50 W/mm. Ga 2 O 3 having unique material
properties and large-size substrate availability (as compared to GaN), which improve
its cost/performance metric over GaN, and finds exclusive applications—high power
RF devices operating at low frequency—military-owned low-frequency high-voltage
application, and AC-to-DC conversion utilities. Ga 2 O 3 based HEMTs achieved CW
output power of 13.7 dBm at 800 MHz with PAE of 6.3%, while small signal cut-off
frequency of 3.3 GHz. Although very low electron mobility and poor thermal conductivity of β-Ga 2 O 3 restrict high power operation due to significant increase in channel
temperature led reduced electron mobility, although highly scaled devices having
ballistic transport may address the issue. It is concluded that GaN- and β-Ga 2 O 3
HEMTs can fully serve the entire RF power electronics application field based on
commercial and technical aspects to choose the perfect one for the right application.
Acknowledgements This publication is an outcome of the R&D work undertaken by the project
under the Visvesvaraya Ph.D. Scheme of Ministry of Electronics and Information Technology
(MeitY), Govt. of India, being implemented by Digital India Corporation. Acknowledgement also
goes to New Jersey Institute of Technology (NJIT), Newark, USA, for facilitating the visit of T. R.
Lenka for collaborative research work.