Experimental evidence of ballistic transport in cylindrical gate-all-around twin silicon nanowire metal-oxide-semiconductor field-effect transistors

Abstract

We have investigated the electrical characteristics of cylindrical gate-all-around twin silicon nanowire metal-oxide-semiconductor field effect-transistors with 4 nm radius and the gate length ranging from 22 to 408 nm. We observed strong transconductance overshoot in the linear source-drain bias regime in the devices with channel length shorter than 46 nm. The mean free path estimated from the slope of the zero-field one dimensional ballistic resistance measured as a function of device length was almost the same as this length.Silicon-based gate-all-around ͑GAA͒ nanowire transistors are considered promising alternatives to planar metaloxide-semiconductor field-effect transistors ͑MOSFETs͒ because of better gate bias control of electron channels and, thus, reduction of various short channel effects. 1,2 These nanowire devices provide another interesting opportunity since they are expected to have unique one-dimensional electron properties when their radius is small enough and scatterings are suppressed.Ballistic electrons do not go through inelastic scattering while traveling across the channel. Earlier, such perfect ballisticity and conductance quantization at cryogenic temperatures were achieved in patterned one-dimensional GaAs/ AlGaAs heterostructures. 3 Recently, transport in carbon nanotubes has exhibited such ballisticity at room temperature due to its one-dimensional nature with smaller inelastic scattering probability. 4 In conventional planar short channel MOSFETs, some of the carriers can pass the channel when they have large enough velocities. In this case, the ratio of the ballistic electrons over the total number of injected electrons is an important factor. 5 So far, not much experimental information has been obtained on such ballistic transport in recently developed three-dimensional ͑3D͒ MOSFETs even though 3D confinement 6 is expected to modify the electron mobilities ͑thus injection efficiencies͒ and energy relaxation mechanisms.In this letter, we report the electrical characteristics of 4 nm radius cylindrical GAA twin silicon nanowire MOSFETs ͑TSNWFETs͒ with various lengths ͑L's͒ ranging from 22 to 408 nm. We have observed strong overshoots in the low-bias transconductance ͑g m ͒ in the devices with L Ͻ 50 nm. We have analyzed this g m data by means of ballistic transport. The mean free path estimated by zero-field one-dimensional ͑1D͒ resistivity measured from the devices with various lengths is compared with the length scales at which the g m overshoot occurs. Figure 1 shows a schematic and a typical transmission electron microscope ͑TEM͒ image of our TSNWFETs fabricated by full complementary MOS ͑CMOS͒ processes. 1 The formation of the twin nanowires was accomplished by selective epitaxial growth of Si 0.77 Ge 0.23 / Si layers and subsequent removal of the SiGe layer. We performed an in situ steam generated ͑ISSG͒ process to grow gate oxide with a thickness of 3.5 nm. Then, the TiN gate material filling was completed. The TEM image clearly confirmed the circular, crystalline nanowire with ...

Current-voltage characteristics for two systems of quantum waveguides with connected quantum resonators

“…Без учета квантового поведения электрона оказывается уже невозможно описать работу устройства. В качестве примеров таких устройств можно привести плоские МОП-транзисторы (planar MOSFET's) [1] и МОП-транзисторы с окружающим затвором (GAA MOSFET's) [2][3][4]. Обе системы тесно связаны с более фундаментальными разработками последних лет: транзисторы с планарным затвором (in-plane-gate transistors) [5], одноэлектронные транзисторы (singleelectron transistors) [6], резонансные туннельные диоды (nanowire resonant tunneling diodes) [7,8].…”

Impact of Precisely Positioned Dopants on the Performance of an Ultimate Silicon Nanowire Transistor: A Full Three-Dimensional NEGF Simulation Study

“…The main reason for this is the 6 nm channel length of our SNWT. We believe that the inclusion of phonon scattering would have little impact on our results for the following reasons: Experiments and simulations of NWTs with 20 nm channel length and above show a high degree of ballisticity [26], [27]. Therefore we expect that nanowires with a channel length of 6 nm will operate close to the ballistic limit.…”

“…Importantly, at channel lengths of sub 10-nm, all of these devices exhibit both strong quantum confinement and significant source-to-drain tunnelling [16], [17]. As a result, drift-diffusion and Monte Carlo simulations methods are not sufficient to describe their behaviour and full-scale quantum transport (QT) simulations are required.…”

“…In particular the gate-all-around nanowire transistors (NWT) with a very small cross-section are very promising due to their excellent electrostatic integrity and scalability down to sub-5 nm dimensions [10]. Indeed such SNWTs have not only been experimentally demonstrated but they have also been the Holy Grail of demonstrating the impact of a single dopant in the channel [11]-[15].Importantly, at channel lengths of sub 10-nm, all of these devices exhibit both strong quantum confinement and significant source-to-drain tunnelling [16], [17]. As a result, drift-diffusion and Monte Carlo simulations methods are not sufficient to describe their behaviour and full-scale quantum transport (QT) simulations are required.…”

Design and Characterization of the Next Generation Nanowire Amplifiers

“…Vertical surrounding gate field effect transistors (SGFETs) have full gate control around channel and have minimized short-channel effects [3]. The elimination of bulk in these transistors reduces latchup and substrate noise.…”