Pierre E. Schmidt

D.C. and high-frequency characteristics of built-in channel MOS-FETs☆

Abstract This paper analyses the d.c. and small-signal a.c. characteristics of MOS-FETs with a built-in conducting channel that can either be completely depleted or enhanced in conductivity by carrier accumulation. The effects of the substrate resistivity are considered for low, moderate and high doping concentrations. It is shown that only when the channel thickness is much smaller than the oxide thickness the device saturation characteristics can be approximated by a square function of the gate voltage. Results of small-signal calculations are presented for both generalized and specific device structures which depict the gate voltage dependence of the gate and substrate transconductance and the input capacitance parameters for both depletion and accumulation mode of operations. A small signal equivalent network model is proposed which can be used for the calculation of high-frequency device limitations.

Switching in organic polymer films

Abstract In this paper we discuss threshold switching effects in thin films of polymethylmethacrylate on molybdenum, silver, copper, graphite, Nesa and Nesatron substrates, using counterelectrodes of pyrolytic graphite. The similarities to corresponding phenomena in multicomponent chalcogenide alloys point to inherently common mechanisms. Lateral variations in switching characteristics are discussed in terms of trap distribution statistics.

High-frequency limitations of abrupt-junction FET's

This paper represents analytical results concerning the high-frequency limitations of FETs of junction-gate or Schottky-gate constructions. The intrinsic y parameters are calculated in closed form using the analog RC transmission line method. The bias dependence of various characteristic factors in the y parameters expressions are presented graphically. Equivalent networks including both the intrinsic and extrinsic resistance-capacitance elements are presented and used to calculate the power-gain and frequency limitations of FETs.

Theoretical and experimental study of the operation of ovonic switches in the relaxation oscillation mode. I. The charging characteristic during the off state

A simple theory of the charging cycle is presented for ovonic switches operating in the relaxation oscillation mode. The theory takes into account the variation of the OFF‐state resistance with bias voltage. An analytical expression for the period of oscillation as a function of circuit components and device parameters is obtained showing that a nonlinear increase of the period of oscillation exists with increasing series resistance. The presented theory is in good agreement with experimental results.

Space‐charge controlled conduction in thick metal‐insulator‐metal barriers

Numerical solutions of the (field and diffusion) transport equations yield energy and concentration contours for thick M1‐I‐M2 (metal‐insulator‐metal) barriers, and their appropriate current‐voltage relationships, with and without traps. Traps must ordinarily be expected in such films, and it is shown that they result in a curvature of the barrier profile, which exercises a controlling influence over I‐V characteristics in the forward direction.

On the wide-range bias dependence of transistor d.c. and small-signal current gain factors

A critical reappraisal is made of the bias dependence of the d.c. and small-signal a.c. current gain factors of planar bipolar transistors over a wide range of currents. This is based on a straightforward consideration of the three basic components of the d.c. base current arising due to emitter-to-base injected minority carrier transport, base-to-emitter carrier injection, and emitter-base surface depletion layer recombination effects. Among other important results it is shown that over a useful bias range the d.c. and small-signal current gain factors, respectively, obey the simple relationships: HFE∞ Ic13 and hfe≈ 1.5hFE Experimental results on representative n-p-n and p-n-p silicon devices are given which support most of the analytical findings.

Drift-diffusion theory of symmetrical double-junction diodes

Abstract Using numerical methods, we have calculated the current-voltage characteristics, energy contours and carrier distributions of a symmetrical double junction diode ( n + nn + and n + pn + ). It is found that the I-V characteristics at low currents and voltages depend greatly on the doping concentration of the base region; at hihg currents, they do not. In that regime, the characteristics bunch together, and can be approximated with remarkable fidelity by the Mott-Gurney law for space-charge controlled conduction in solids. Characteristics are presented for different impurity densities and base widths.

The operation of thin film chalcogenide glass threshold switches in the relaxation oscillation mode

In this paper we report on the operation of thin films of Te40As35Ge7Si18 in the relaxation oscillation mode. The period of oscillation was measured as a function of series resistance for various d.c. bias voltages. The statistical character of threshold switching in the devices is manifested by large fluctuations in the period of the relaxation oscillations. Large differences in the period are observed when the polarity of the d.c. bias voltage is reversed, suggesting the occurence of forming processes.

Single‐carrier space‐charge controlled conduction

Single‐carrier space‐charge controlled conduction in metal‐insulator‐metal structures has been studied. The dc J‐V characteristics have been calculated over an extended range of current for insulator films of different thicknesses with and without traps. It is found: (i) The current is proportional to voltage at low currents, the proportionality factor depending on the injecting contact carrier concentration, insulator thickness, and trap density. (ii) At moderate currents, the J‐V characteristics can be approximated only over a limited range of currents by a power law with the exponent n depending on the injecting contact carrier concentration, insulator thickness, and trap content. (iii) At high currents the conduction is ohmic and the characteristics are identical for insulators with or without traps. The special case of identical carrier concentrations at both contacts is also discussed. It is found that in this particular case the square law in voltage and the cubic dependence in thickness become onl...

Theoretical and experimental study of the operation of ovonic switches in the relaxation oscillation mode. II. The discharging characteristics and the equivalent circuits

We describe that part of the relaxation oscillation cycle during which the ovonic device will switch from a high resistance OFF state to a lower conductance ON state, either as a time‐varying resistance or through a nonlinear intermediate negative resistance state. We discuss in detail several equivalent circuits that describe the observed experimental behavior.