Y-function Method Research Articles

The Comparison of Various S/D Series Resistances Methods for Deeply Submicron MOSFETs

Accurate extraction of source/drain series resistance (Rs/Rd ) is crucial to the modeling and application of deeply scaled MOSFET devices. In this study, we investigate three methods of extracting source/drain series resistance for deep submicron MOSFETs, including the Y-function method, the trans-conductance method and the direct I-V method. The results show that resistance obtained from direct I-V method is smaller than both trans-conductance method and Y function method. Theory analysis illustrate that the trans-conductance method and Y-function method give an overestimation of resistance due to the neglect of the mobility degradation under the relative high gate voltage. Relatively, direct I-V method is a promising method for estimating source/drain resistance in deep submicron MOSFETs.

Static and low frequency noise characterization of N-type random network of carbon nanotubes thin film transistors

Static and low frequency noise (LFN) characterizations in two-dimensional (2D) N-type random network thin film transistors (RN-TFTs) based on single-walled carbon nanotubes were presented. For the electrical parameter extraction, the Y-function method was used to suppress the series resistance (Rsd) influence. The gate-to-channel capacitance (Cgc) was directly measured by the split capacitance-to-voltage method and compared to 2D metal-plate capacitance model (C2D). In addition, to account for the percolation-dominated 2D RN-TFTs, a numerical percolation simulation was performed. LFN measurements were also carried out and the results were well interpreted by the carrier number and correlated mobility fluctuation model. Finally, one-dimensional (1D) cylindrical analytical capacitance based model (C1D) was suggested and applied to provide better consistency between all electrical parameters based on experimental and simulation results.

Direct evaluation of low-field mobility and access resistance in pentacene field-effect transistors

Organic field-effect transistors (OFETs) suffer from limitations such as low mobility of charge carriers and high access resistance. Direct and accurate evaluation of these quantities becomes crucial for understanding the OFETs properties. We introduce the Y function method (YFM) to pentacene OFETs. This method allows us to evaluate the low-field mobility without the access or contact resistance influence. The low-field mobility is shown to be more appropriate than the currently applied field-effect mobility for the OFETs’ performance evaluation. Its unique advantage is to directly suppress the contact resistance influence in individual transistors, although such contact resistance is a constant as compared to the widely accepted variable one with respect to the gate voltage. After a comparison in detail with the transmission-line method, the YFM proved to be a fast and precise alternative method for the contact resistance evaluation. At the same time, how the contact resistance affects the effective mobility and the field-effect mobility in organic transistors is also addressed.

The influence of HfO 2 film thickness on the interface state density and low field mobility of n channel HfO 2/TiN gate MOSFETs

The influence of HfO 2 thickness (1.6 to 3nm) on interface state density and low field mobility in HfO 2/TiN gate n channel MOSFETs have been studied by analyzing experimental data from charge pumping, split CV, DC I d- V g, pulsed I d- V g and Y-function methods. It is found that there is no HfO 2 thickness dependence on the interface state density, whereas there is continuous electron mobility degradation with HfO 2 thickness. The devices exhibited no detectable fast transient charge trapping, allowing the relative contributions of phonon and Coulomb scattering to be examined over temperature. The dependence of the low field mobility on temperature from 50 K to 400 K indicates HfO 2 remote phonon scattering as the dominant cause of the mobility degradation.

DIFFUSE LEED INTENSITY CALCULATIONS TAKING INTO ACCOUNT THE PAIR CORRELATION EFFECTS IN PARTIALLY ORDERED OVERLAYER

The elastic diffuse intensity of electrons scattered by a short-range-ordered adlayer depends on the structure factors and on renormalized t matrices for each kind of occupied bonding sites. In many cases, the computation of these structure factors is a crucial point for the application of the general DLEED theory. Their determination necessitates the knowledge of the site-occupancy pair correlation functions. Up to now two procedures removing pair correlation effects from the data have been used for DLEED intensity calculations. The first procedure, the Y-function method, can be applied only in the particular case where there is one kind of chemisorption site. The second one was proposed recently and is based on the sampling of diffuse LEED intensity distributions by conventional spot intensities. The aim of this paper is to study DLEED intensity distribution coming from the sampling method and from the general treatment of DLEED taking into account the pair correlation effects. We take as an example the Pt(111)/CO system. The site-occupancy pair correlation functions of CO adsorbed on Pt(111) are obtained by a Monte Carlo simulation. DLEED intensities are analyzed using the energy-dependent I–V curves.