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We propose a unified DC and flicker noise model for bottom-gate amorphous InGaZO (a-IGZO) thin film transistors (TFTs) with an etch stop layer (ESL) valid for subthreshold, linear, and saturation regimes. A recent study carried out by our group about the origin of 1/f noise in four ESL a-IGZO TFTs with gate lengths 15, 20, 30, and 50 μ m and a width of 100 μ m revealed that carrier number fluctuation is the dominant mechanism of flicker noise in these specific devices and the contact resistances do not significantly contribute to the overall noise level. In this paper, we extended the work to develop a physics based 1/f noise model for ESL a-IGZo TFTs. The unified model and parameter extraction method, a technique developed for accurate parameter extraction and modeling of TFT device characteristics, is adapted to develop the I-V model. The noise model is subsequently derived taking into account the observed correlated mobility fluctuation based on the unified 1/f noise modeling idea. Results showed an excellent agreement between the experimental and modeled data for both the DC and flicker noise behavior of sample ESL a-IGZO TFTs over a broad range of bias conditions, at 298, 315, and 333 K operating temperatures.

We explore the prospective behavior of the nanoscale double-gate metal-oxide-semiconductor field-effect-transistor (DG-MOSFET) when used as the basis for building analog circuits. Results for transconductance, output conductance, and related parameters, such as transconductance efficiency, and Early voltage, are presented in the ballistic and diffusive regimes using the non-equilibrium Green’s function method (NEGF) and the scattering theory of the nanoscale MOSFET. Very high transconductance (∼20mS∕μm), approaching the ballistic limit, can be achieved provided that technological improvements further increase the electron mobility in the silicon film. For the ballistic limit a cutoff frequency of about 1–4THz is possible. The transconductance efficiency is not to much affected by length scaling and temperature. The output conductance and Early voltage are severely affected by length scaling as channel length-modulation (CLM) and drain-induced barrier lowering (DIBL) effects become more important, but they...

In this paper we extend a compact surrounding-gate MOSFET model to include the hydrodynamic transport and quantum mechanical effects, and we show that it can reproduce the results of 3D numerical simulations using advanced transport models. A template device representative for the cylindrical surrounding-gate MOSFET was used to validate the model. The final compact model includes mobility degradation, drain-induced barrier lowering, velocity overshoot, and quantum effects. Comparison between the compact model and the advanced transport modeling approaches shows good agreement within the practical range of drain voltages.

In this work, we report on Monte Carlo simulations to study the capability to generate Gunn oscillations of diodes based on InP and GaN with around 1 lm active region length. We compare the power spectral density of current sequences in diodes with and without notch for different lengths and two doping profiles. It is found that InP structures provide 400 GHz current oscillations for the fundamental harmonic in structures without notch and around 140 GHz in notched diodes. On the other hand, GaN diodes can operate up to 300 GHz for the fundamental harmonic, and when the notch is effective, a larger number of harmonics, reaching the Terahertz range, with higher spectral purity than in InP diodes are generated. Therefore, GaN-based diodes offer a high power alternative for sub-millimeter wave Gunn oscillations., European Commision (EC). Funding FP7/SP1/ICT. Project Code: 243845

In this work, we report on Monte Carlo simulations of InP and GaN vertical Gunn diodes to optimize their oscillation frequency and DC to AC conversion efficiency. We show that equivalent operating conditions are achieved by the direct application of a sinusoidal AC voltage superimposed to the DC bias and by the simulation of the intrinsic device coupled with the consistent solution of a parallel RLC resonant circuit connected in series. InP diodes with active region about 1 μm offer a conversion efficiency up to 5.5% for frequencies around 225 GHz. By virtue of the larger saturation velocity, for a given diode length, oscillation frequencies in GaN diodes are higher than for InP structures. Current oscillations at frequencies as high as 675 GHz, with 0.1% efficiency, are predicted at the sixth generation band in a 0.9 μm-long GaN diode, corroborating the suitability of GaN to operate near the THz band. At the first generation band, structures with notch, in general, provide lower oscillation frequencies and efficiencies in comparison with the same structures without notch. However, a higher number of generation bands are originated in notched diodes, thus, typically reaching larger frequencies. Self-heating effects reduce the performance, but in GaN diodes the efficiency is not significantly degraded.

10.1063/1.4733465 Temperature dependence of THz detection by field effect transistors was investigated in a wide range of temperatures from 275 K down to 5 K. The important increase of the photoresponse following 1/T functional dependence was observed when cooling from room temperature down to 30 K. At the temperatures below ∼30 K, the THz response saturated and stayed temperature independent. Similar behavior was observed for GaAs, GaN, and Si based field effect transistors. The high temperature data were successfully interpreted using recent theory of overdamped plasma excitation in field effect transistors. The low temperature saturation of the photoresponse was tentatively explained by the change of the transport regime from diffusive to ballistic or traps governed one. Our results clearly show that THz detectors based on field effect transistors may improve their responsivity with lowering temperature but in the lowest temperatures (below ∼30 K) further improvement is hindered by the physics of the electron transport itself

[EN] We present a Monte Carlo time-domain study of nanostructured ballistic three-branch junctions (TBJs) excited by both step-function and Gaussian picosecond transients. Our TBJs were based on InGaAs 2-dimensional electron gas heterostructures and their geometry followed exactly the earlier experimental studies. Time-resolved, picosecond transients of both the central branch potential and the between-the-arms current demonstrate that the bandwidth of the intrinsic TBJ response reaches the THz frequency range, being mainly limited by the large-signal, intervalley scattering, when the carrier transport regime changes from ballistic to diffusive., ROOTHz (FP7-243845)

Under certain conditions, plasma instabilities associated with streaming motion of carriers taking place in n+nn+ diodes can lead to current oscillations. The origin of the phenomenon, known as optical phonon transit time resonance, is characterized by a frequency related to the transit time between consecutive optical phonon emissions by electrons along the active region of the diode. By means of Monte Carlo simulations, the possibility to obtaining current oscillations in GaN n+nn+ diodes is analyzed. The optimum conditions for the onset of such mechanism are investigated: applied bias, temperature, doping, and length of the active n region. Simulations show that current oscillations at frequencies in the terahertz range can be obtained at very low temperatures. Moreover, by choosing the appropriate applied voltage and length of the n region, some degree of tunability can be achieved for frequencies close to the plasma frequency of the n region of the n+nn+ diode.

The surrounding gate (SGT) metal-oxide-semiconductor field-effect transistor is one of the most promising candidates for the downscaling of complementary metal-oxide-semiconductor technology toward the sub-50-nm channel length range since the SGT architecture allows excellent control of the channel charge in the silicon film, thus reducing short channel effects. However, at these dimensions, quantum effects must be considered in order to develop accurate compact models useful for circuit simulations. In this paper we study the influence of quantum effects on dc, radio frequency (rf), and microwave noise for nanoscale SGT transistors including nonstationary effects. We present an analytical charge model for adjusting the charge control computed from the self-consistent solution of the two-dimensional Schrodinger and Poisson equations. rf and noise performances are calculated using the active transmission line method. We compared, on the one hand, classical and quantum charge control models and, on the othe...

Silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs) are excellent candidates to become an alternative to conventional bulk technologies. The most promising SOI devices for the nanoscale range are based on multiple gate structures such as double-gate (DG) MOSFETs. These devices could be used for high-frequency applications due to the significant increase in the transition frequency fT for these devices. For low noise radiofrequency and microwave applications, high-frequency noise models are required. In this work, we present compact expressions to model the drain and gate current noise spectrum densities and their correlation for DG MOSFETs. These expressions depend on the mobile charge densities that are obtained using analytical expressions obtained from modeling the surface potential and the difference of potentials at the surface and at the center of the Si doped layer without the need to solve any transcendental equations. Using this model, the DG MOSFET noise perfo...

Fin-shaped field effect transistors (FinFETs) are considered to be a very attractive option to improve the performance of complementary metal-oxide-semiconductor devices into the sub-50‐nm gate length regime. However, for those dimensions, quantum effects must be considered in order to develop accurate compact models useful for circuit simulations. In this paper, we study the influence of the quantum effects on dc, Radio frequency (rf), and microwave noise for nanoscale FinFET transistors including nonstationary effects. We present an analytical charge model to adjust the charge control computed from the self-consistent solution of the two-dimensional Schrodinger and Poisson equations. rf and noise performances are calculated using the active transmission line method. Comparison between classical and quantum charge control and between drift-diffusion and hydrodynamic models is carried out.

In this paper, we present an analytical model for high frequency and microwave noise model of nanoscale double-gate metal-oxide-semiconductor field-effect transistor. The model is based on a compact model for charge quantization within the channel and it includes overshoot velocity effects. Radio-frequency and noise performances are calculated using an active transmission line method. A comparison is made between classical and quantum charge control and between drift diffusion and hydrodynamic models.