Periodic Reporting for period 2 - DYNAMISM (Dynamic Properties of Ferroelectric III-V MOSFETs)
Reporting period: 2023-03-01 to 2024-08-31
The discovery of ferroelectric characteristics in annealed HfO2–based films opens a wide range of applications not only in
memory and logic, but the results will enable new scientific directions for instance in reconfigurable electronics. So far,
ferroelectric films have been investigated in metal-insulator-metal structures suitable for back-end-of-line integration. They
have also been introduced onto Si and two-dimensional materials. However, there is a gap of knowledge with lack of science
and technology for integration of HfO2–based ferroelectric films on III-V channel materials where the increased permittivity
will improve electrostatics. III-V transistors hold a key position for high-performance millimetre wave electronics. The high
electron mobility in III-V materials contributes to a high transconductance that enables high unity-current-gain cut-off
frequency and unity-power-gain cut-off frequency, fT and fmax, more than a factor 3 higher than competing Si MOSFET
technologies. The wide options for heterostructure design have enabled III-V steep-slope transistors for low-power
electronics operating down to 30 mV/dec without hysteresis .
To research for the first time ferroelectric films integrated on high-performance III-V devices at technology-relevant
dimensions, we will use our demonstrated integration of Hf0.5Zr0.5O2 on InAs:
- Establishing the best strategy to integrate ferroelectric gate-stacks on III-V materials with strong polarization and
long endurance.
- Characterizing the dynamic properties with non-volatile functionality of ferroelectric films integrated on III-V transistor
channels.
- Investigating ferroelectric III-V MOSFETs for future applications including millimeter-wave devices, cryogenic
electronics, Negative Capacitance FET (NC-FET) circuitry, and Ferroelectric Tunnel Junctions (FTJs).
Combined, the new science and technology will enable novel high-performance devices as well as reconfigurable millimetrewave
electronics.
memory and logic, but the results will enable new scientific directions for instance in reconfigurable electronics. So far,
ferroelectric films have been investigated in metal-insulator-metal structures suitable for back-end-of-line integration. They
have also been introduced onto Si and two-dimensional materials. However, there is a gap of knowledge with lack of science
and technology for integration of HfO2–based ferroelectric films on III-V channel materials where the increased permittivity
will improve electrostatics. III-V transistors hold a key position for high-performance millimetre wave electronics. The high
electron mobility in III-V materials contributes to a high transconductance that enables high unity-current-gain cut-off
frequency and unity-power-gain cut-off frequency, fT and fmax, more than a factor 3 higher than competing Si MOSFET
technologies. The wide options for heterostructure design have enabled III-V steep-slope transistors for low-power
electronics operating down to 30 mV/dec without hysteresis .
To research for the first time ferroelectric films integrated on high-performance III-V devices at technology-relevant
dimensions, we will use our demonstrated integration of Hf0.5Zr0.5O2 on InAs:
- Establishing the best strategy to integrate ferroelectric gate-stacks on III-V materials with strong polarization and
long endurance.
- Characterizing the dynamic properties with non-volatile functionality of ferroelectric films integrated on III-V transistor
channels.
- Investigating ferroelectric III-V MOSFETs for future applications including millimeter-wave devices, cryogenic
electronics, Negative Capacitance FET (NC-FET) circuitry, and Ferroelectric Tunnel Junctions (FTJs).
Combined, the new science and technology will enable novel high-performance devices as well as reconfigurable millimetrewave
electronics.
The first work package WP1 “Ferroelectric III-V gate-stacks” addresses the integration and investigation of ferroelectric HZO films on III-V substrates and nanowires building on our demonstrated high polarization of HZO on InAs. We have within WP1 continued to evaluate the ferroelectric properties of HZO on InAs and extended the studies to include both interface evaluation with determination of the interface charge densities, the introduction of nano-laminated material to further reduce the crystallization temperature, and the introduction of Zr-rich HZO to increase the permittivity and to shift towards anti-ferroelectric properties. The results demonstrate a wide process window for the material integration where various strategies can be applied and still achieve strong polarization effects.
WP2 “Ferroelectric RF-Devices “ we investigate the dynamic properties of ferroelectric gate-stacks will be characterized by quasi-static and RF-measurements. Here, the HZO-films have successfully been integrated on vertical III-V nanowire devices, both in form of InAs MOSFETs and InAs/GaSb TunnelFETs. The ferroelectric MOSFETs show a healthy memory window of about 1-2V, endurance of 10^4 cycles and useful drive currents. A major breakthrough is the finding that ferroelectric HZO is easier to integrate on the InAs/GaSb TunnelFET device structure. Combining the evaluation of the ferroelectric switching mechanism and the tunneling properties has allowed us to in detail study the operation of individual domain switching in the film. By careful design of pulse sequences we are able to determine the difference between one, two, three and four participating switching domains. Furthermore we have evaluate the GHz switching dynamics on planar MOSCAP reference structures with demonstration of varactor-like capacitance modulation up to 60 GHz and real-time domain switching speed of 1 ns.
In WP3, we have used the ferroelectric TunnelFETs for analogue operation using a negative differential transconductance in the forward operation of the TunnelFET. By shifting the polarization state, the peak voltage can be modulated with operation as either a pass-transistor or a frequency doubler. Further adjustments enabled also a phase shifter operation. Finally, the first generation of small-signal models for the ferroelectric operation has been developed and introduced into ADS simulation environment. Layouts and simulation of ferroelectric switches has been developed and the circuits are waiting for fabrication.
WP2 “Ferroelectric RF-Devices “ we investigate the dynamic properties of ferroelectric gate-stacks will be characterized by quasi-static and RF-measurements. Here, the HZO-films have successfully been integrated on vertical III-V nanowire devices, both in form of InAs MOSFETs and InAs/GaSb TunnelFETs. The ferroelectric MOSFETs show a healthy memory window of about 1-2V, endurance of 10^4 cycles and useful drive currents. A major breakthrough is the finding that ferroelectric HZO is easier to integrate on the InAs/GaSb TunnelFET device structure. Combining the evaluation of the ferroelectric switching mechanism and the tunneling properties has allowed us to in detail study the operation of individual domain switching in the film. By careful design of pulse sequences we are able to determine the difference between one, two, three and four participating switching domains. Furthermore we have evaluate the GHz switching dynamics on planar MOSCAP reference structures with demonstration of varactor-like capacitance modulation up to 60 GHz and real-time domain switching speed of 1 ns.
In WP3, we have used the ferroelectric TunnelFETs for analogue operation using a negative differential transconductance in the forward operation of the TunnelFET. By shifting the polarization state, the peak voltage can be modulated with operation as either a pass-transistor or a frequency doubler. Further adjustments enabled also a phase shifter operation. Finally, the first generation of small-signal models for the ferroelectric operation has been developed and introduced into ADS simulation environment. Layouts and simulation of ferroelectric switches has been developed and the circuits are waiting for fabrication.
The progress so far clearly demonstrates successful integration of ferroelectric HZO on III-V materials including vertical III-V nanowires. Various types of non-volatile and ferroelectric transistors have been demonstrated and reported including DC characteristics and ferroelectric polarization switching characteristics. Initial results on dynamic properties at higher frequencies have been obtained and it is expected that further results on the RF-properties will be generated as the device structures will be more developed and targeted towards the high-frequency characterization.