Comparative study of vertical GAA TFETs and GAA MOSFETs in function of the inversion coefficient

Sivieri, V. B.; Agopian, Paula Ghedini Der; Martino, João Antônio; Rooyackers, R.; Vandooren, A.; Simoen, Eddy; Thean, Aaron; Claeys, Cor

doi:10.1109/ulis.2016.7440087

Cited by 4 publications

(5 citation statements)

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“…The measured MOSFETs have only Si in the channel, source, and drain regions. The isolated characteristics of the transistors have already been extensively studied in previous works [21][22][23][24][25][26]. A schematic of the devices is shown in figure 1.…”

Section: Devices Descriptionmentioning

confidence: 99%

“…The transistors used in this study have already been extensively studied at a device level [18][19][20][21][22][23][24][25][26], but not at circuit level. Therefore, a simple, well-known topology was chosen so that the characteristics of the different devices and its effects in the OTA performance can be analyzed without worries about circuit complexity.…”

Section: Introductionmentioning

confidence: 99%

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Operational transconductance amplifier designed with nanowire tunnel-FET with Si, SiGe and Ge sources using experimental data

Nogueira

Agopian

Martino

2020

Semicond. Sci. Technol.

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In this paper operational transconductance amplifiers (OTA) were designed with nanowire (NW) tunnel field effect transistors (TFET) with different source materials (Si, SiGe, and Ge) and compared with NW Si MOSFET devices. Lookup tables with experimental data were used to model the transistors and simulate the OTAs. At the same dimensions and transistor efficiency region, the TFET OTAs have larger gain than the MOSFET circuit. The Ge-source TFET OTA presents the highest differential gain (105 dB), followed by the Si TFET (96 dB) and the SiGe-source TFET (90 dB), with the MOSFET presenting the lowest gain (51 dB). However, the MOSFET has the best gain-bandwidth product (GBW) (9.2 MHz) followed by the Ge-source TFET (1.6 MHz), the SiGe-source TFET (900 kHz) and the Si TFET (41 kHz). The second group of OTAs, where the same power consumption was considered and where the gain of the MOSFET OTA and the GBW of the TFETs' circuits were increased was also studied. The gain of the MOSFET OTA increased to 56 dB, but it is still lower than the TFET circuits (96, 90 and 102 dB for the Si TFET, SiGe-source TFET and Ge-source TFET, respectively). The GBW of the Si TFET, SiGe-source TFET and Ge-source TFET circuits increased to 71 kHz, 1 MHz, and 2 MHz, respectively. Nevertheless, the MOSFET OTA has the best GBW (4.7 MHz) again but being just 2.35 times the GBW of the Ge-source TFET case. Therefore, because of the high gain of the TFETs OTAs, they are indicated for low power, low-frequency applications, with the Ge-source TFET presenting a good compromise between gain and GBW. The circuits' linearity was also verified, and they demonstrate to be more dependent on bias choices than on the devices themselves.

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Section: Devices Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operational transconductance amplifier designed with nanowire tunnel-FET with Si, SiGe and Ge sources using experimental data

Nogueira

Agopian

Martino

2020

Semicond. Sci. Technol.

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“…Fonte: [53] No gráfico apresentado na figura 2.22, pode-se observar os diferentes regimes de condução e os coeficientes de inversão referentes a cada uma dessas regiões.…”

Section: Inversão Fracaunclassified

“…No tocante aos TFETs, o de junção abrupta possui um valor de gm maior do que o de junção não-abrupta. Fonte: [53] Observa-se que o valor máximo obtido para o coeficiente de inversão no caso do TFET foi aproximadamente 1, devido ao alto valor utilizado para a tensão de limiar. Outro parâmetro analisado foi a frequência de ganho unitário, que pode ser calculada com base na seguinte equação:…”

Section: D=30nmunclassified

Estudo de transistores de tunelamento induzido por efeito de campo (TFET) construídos em nanofio.

Sivieri¹

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This Master thesis focused in the study of the NW-TFET. The study was performed either by simulation as by experimental measurements. The main digital and analog characteristics of the device and its potential for use in advanced integrated circuits for the next decade were studied. The analysis was performed by extracting and studying the devices main parameters, such as subthreshold swing, transconductance (gm), output conductance (gd), intrinsic voltage gain (AV) and transistor efficiency. The experimental measurements were compared with the results obtained by simulation. Utilizing different simulation fitting parameters and models, the device behavior (observed in the experimental measurements) was understood and explained. During the execution of this work, either the influence of the source material on the device performance, as the impact of the nanowire diameter on the transistor main analog parameters, were studied. The devices with SiGe source presented higher values of gm and gd than those with silicon source. The percentual difference among the values of transconductance for the different source materials varied from 43% to 96%, being dependent on the method utilized for the comparison, and the percentual difference among the values of output conductance varied from 38% to 91%. A degradation of AV was also observed with the nanowire diameter reduction. The gain calculated from the experimental measurements for the device with 50 nm of diameter is approximately 57% lower than the gain corresponding to the diameter of 110 nm. Furthermore, the impact of the diameter considering different gate biases (VG) was analysed. It was concluded that TFETs show improved performance for lower values of VG (a reduction of approximately 88% of AV was observed for an increase of the gate voltage from 1.25 V to 1.9 V). The gate/source overlap length and the dopant profile at the tunneling junction were also analyzed in order to understand which combination of this features would result in a better performance of the device. It was observed that the best results were related to an alignment between the gate electrode and the source/channel junction and to an abrupt dopant profile at the junction. Finally, the MOS technology was compared with TFET, resulting in a higher AV (higher than 40 dB) for the TFET.

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“…O ponteiro "High" foi ligado à porta e um sinal senoidal com frequência igual a 10 kHz, junto a uma polarização em corrente contínua (CC), foi aplicado. Ao medir a corrente obtida no terminal "Low" o equipamento calcula a capacitância diferencial em função de VG.Estes dispositivos já foram extensivamente estudados a nível de dispositivo e mais detalhes sobre suas características podem ser encontrados em Martino et al(2015),Bordallo et al (2015Bordallo et al ( , 2016,Agopian et al (2015) eSivieri et al (2016).3.2 VERILOG-A E MODELAGEM ATRAVÉS DE LOOKUP TABLEA modelagem através de LUT consiste em escrever uma função através de pontos discretos em uma tabela ao invés de utilizar uma expressão matemática contínua. Esse artifício pode ser utilizado quando não se possui um modelo analítico compacto que permita a simulação de circuitos complexos, sendo ideal no caso de novos nós tecnológicos ou no caso de novos dispositivos onde a sua física ainda não é totalmente compreendida (ROFOUGARAN;FURMAN;ABIDI, 1988).…”

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Estudo de amplificadores operacionais de transcondutância projetados com túnel-FETs e MOSFETs fabricados em estruturas de nanofios

Nogueira¹

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Tunnel Field Effect Transistors (TFET) have gained great interest by the academy in the recent years due to the possibility of achieving subthreshold slopes lower than 60 mV/dec, that is the theoretical limit of the MOSFET in room temperature. This is possible thanks to its main conduction mechanism based on band to band tunneling. This work intends to study operational transconductance amplifiers (OTA) designed with nanowire TFETs with different source materials (Si, SiGe and Ge) to verify its advantages and disadvantage in relation to nanowire silicon MOSFETs (channel length of 220 nm). Experimental measurements were used to create lookup tables that are used to model the devices through the Verilog-A language. By using the software Spectre, from Cadence, the models were initially used to perform basic analog integrated circuit simulations like current mirror, common source amplifier and differential amplifier. The effect of the gate current (IG) in two-stage amplifiers was also verified, showing that extra attention is required regarding the circuit bias, especially in the cases of Si and Ge-source TFETs. Finally, different OTAs were designed using the different technologies and compared. All the TFET OTAs presented a voltage gain superior to the MOSFET circuit, being at least 34 dB larger in all configurations considered, with the circuit projected with the Ge-source TFET presenting the largest voltage gain (105 dB). All the TFET OTAs have a power consumption at least one order of magnitude smaller (Ge-source) than the MOSFET circuit, being able to consume up to three orders less power (Si-source) in circuits with the same size and biased at the same transistor efficiency (gm/ID). However, the MOSFET circuit has a bandwidth-gain product (GBW) of at least one order of magnitude larger than the TFET OTAs. For circuits with the same power consumption and with an increase in the voltage gain of the MOSFET OTA as a project goal, the circuits with TFET with SiGe and Ge-source have a GBW (1 MHz and 2 MHz) in the same order of magnitude than the MOSFET OTA (4,7 MHz). Therefore, the TFETs studied have presented advantages in applications of low power and low frequency, in special the TFET with Ge source have presented a good compromise between gain and GBW and the Si TFET that has a voltage gain comparable to the Ge-source TFET, while consuming less power.

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Comparative study of vertical GAA TFETs and GAA MOSFETs in function of the inversion coefficient

Cited by 4 publications

References 10 publications

Operational transconductance amplifier designed with nanowire tunnel-FET with Si, SiGe and Ge sources using experimental data

Operational transconductance amplifier designed with nanowire tunnel-FET with Si, SiGe and Ge sources using experimental data

Estudo de transistores de tunelamento induzido por efeito de campo (TFET) construídos em nanofio.

Estudo de amplificadores operacionais de transcondutância projetados com túnel-FETs e MOSFETs fabricados em estruturas de nanofios

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