Two-transistor Model Research Articles

DYNAMIC PROPERTIES OF THYRISTORS

In this work the dynamic properties of thyristors are considered. The property of the p-n barrier is briefl y reviewed and the principle of thyristor turn-on by means of a two-transistor model explained, along with an illustrative graphic interpretation of the basic equation. Described next are the dynamic properties of thyristors with a more detailed analysis of the du/dt and di/dt effects and the dynamic turn-on process.

A model for the resonant tunneling semiconductor-controlled rectifier

A new switch called a resonant-tunneling-semiconductor-controlled rectifier (RT-SCR) has been proposed. A two-transistor model is used for the device. One of the transistors in the two-transistor model is assumed to be a resonant tunneling transistor (RTT), while the other transistor is taken to be a bipolar transistor. The current–voltage relationships of the device have been numerically obtained and compared with the traditional thyristor characteristics. The new device requires smaller turn-on gate voltage than a comparable traditional device for the same gate current. This indicates that in comparison with the traditional thyristor, a smaller control current may be used to turn on the device at a particular voltage.

Asymmetric fingered polysilicon p-channel thin film transistor structure for kink effect suppression

We present, for the first time, the application of the asymmetric fingered thin film transistor (AF-TFT) architecture to self-aligned p-channel TFTs for kink effect suppression. In AF-TFT the transistor channel region is split into two zones with different lengths ( L 1 > L 2) separated by a floating p + region. A fourth electrode, contacting the floating p + region, allowed us to measure the individual electrical characteristics of the two sub-TFTs. Output characteristics show that substantial kink effect reduction can be achieved when the sub-TFT placed at the drain end of the device has an L 2 ≪ L 1. The electrical characteristics were analysed by using numerical simulations in the framework of the two-transistor model and we show that kink effect suppression arises from the operation in saturation regime of the source sub-TFT. The electrical characteristics of the fabricated p-channel AF-TFTs show a complete kink effect suppression, making these devices very attractive for current drivers in organic light emitting displays.

Distribution and Impact of Local Trapped Charges in Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) Memory

In this paper we propose a two-transistor model with an RPT for the punch-through resistor in the silicon-oxide-nitride-oxide-silicon (SONOS) memory cell. With this model, the subthreshold leakage current induced by the local trapped charges in silicon nitride and the impact on the cell's read characteristics are studied. Some solutions to decrease this leakage current and change the distribution of the trapped charges are proposed and analyzed, including programming condition optimization, the channel initiated secondary electron (CHISEL) programming, and cell structure optimization. Moreover, using the CHISEL or channel hot electron (CHE) programming, the influences on the programming and the erase characteristics of different charge distributions are investigated.

The silicon p-n-p-n switch and controlled rectifier (thyristor)

Based on the two-transistor model of Jim Ebers (a p-n-p transistor driving an n-p-n, and the n-p-n driving the p-n-p), the two-terminal and three-terminal Si p-n-p-n switch (low power) originated at Bell Telephone Laboratories (BTL) in 1954-1955. The two-terminal version, with its various limitations (along with tile Si technology supplied by BTL, Moll's group), went with Shockley to the West Coast. The two-terminal device and the Shockley enterprise failed, except as an unplanned, unpredicted transfer of technology that accidentally launched Silicon Valley. The three-terminal p-n-p-n device introduced by GE (1957) as the Si controlled rectifier (SCR, later thyristor) succeeded from the beginning, however, and became the dominant control device in the power industry. The early history of this work (1954-1960), including the shorted-emitter and symmetrical switch (TRIAC), is described. The early work proved the need to employ, besides the basic vertical p-n-p-n layering, lateral p-n patterning and the use of the lateral geometry for three-terminal operation, shorted emitters, symmetrical switches (TRIACs), regenerative gate operation, and ultimately gate-turn-off switches. Indeed, the two-terminal device could not match the performance of the three-terminal p-n-p-n switch, which became the premier megawatt control device of the power industry.

An analytic model of holding voltage for latch-up in epitaxial CMOS

For epitaxial CMOS in the latched state, the region between the anode and the cathode is conductivity modulated. In this case, the two-transistor model for the silicon-controlled rectifier (SCR) is not valid. However, a simplified analysis is possible because the well-substrate junction is obliterated by carriers. With this approach an analytic model is developed which can predict the holding voltage and its dependence on design parameters. The model is capable of predicting quantitatively the improvement in holding voltage with increased n+ -to-p+ spacing, thinner epi, substrate backbias, shallow trench, and silicided junctions and higher epi doping. The model explains a previously observed scaling law for the holding voltage.

Nonlinear resonance and parametric phenomena in a complicated oscillating circuit

Nonlinear resonance and parametric phenomena in an oscillating circuit with two nonlinear opposite reactive elements and negative resistance are presented. The examination has been performed on the basis of a nonlinear oscillating circuit represented by a two-transistor model of a pnpn-type device with nonlinear inductance and negative resistance and a self bias pn junction with nonlinear capacitance and a nonlinear conductance.

Turn-on phenomena in optically and electrically fired thyristors

An analytical solution of the time-dependent transport equation including surface recombination and optical injection for a diffused thyristor base is presented. By means of the classical two-transistor model, the turn-on transient may be predicted. Apart from the influence of technological parameters like base width, doping profile, and diffusion length, the effect of optical versus electrical injection as well as surface recombination are discussed. Surface recombination may significantly influence the optical turn-on threshold. Despite the rigorous simplicity of the model, the dynamic turn-on behavior of an optically fired high-voltage thyristor is in very good agreement with the experiment. The data, being presented for a wide range of parameters, are useful for practical design.

An experimental and theoretical analysis of double-diffused MOS transistors

An experimental and theoretical study of double-diffused MOS transistors (DMOST's) has been made. A simple, analytic two-transistor model gives insight into DMOS device physics as well as predicting DMOST characteristics. Both the model and experimental results show that three distinct regions of operation exist: short-channel control, long-channel control, and carrier velocity saturation control. Quantitative criteria are established for judging the region of operation as a function of device parameters and terminal voltages. A DMOST may be optimized to have the same d.c. characteristics as its short-channel component transistor over most of its operating range. A two-transistor model suitable for Computer-Aided Circuit Design (CAD) is also presented.