Design criteria of triode-like JFET's are studied by fully utilizing two-dimensional numerical analysis. The current is caused by tlie carriers injected over a potential barrier in a depleted channel. In contrast to normal pentode-like FET'S, the drain field plays an important role reducing the barrier height and thus causing triode-like I-V characteristics. Triode-like characteristics depend strongly on device geometry. This operation can be realized only in short gate devices. The channel thickness a is an essential parameter in determining the operational mode. The devices operate as triodes or pentodes corresponding to thin or thick channels, respectively. If applied to low-resistance load direct-drive circuits, the mixed characteristics situated between the triode- and pentode-like ones, are more desirable when compared to pure triode-like ones, This is because of their low on-resistance and high ac power efficiency. The gate-drain distance l gd is also essential in determining breakdown voltage. The design criteria are discussed and an optimum design specified on the N D (channel doping)- a and N_{D} - l_{gd} planes with respect to triode-like characteristics, circuit application and breakdown phenomena. Calculated results are compared with experiments and good agreement is found without using any adjustable parameters. The present design criteria will be useful for designing triode-like JFET's.

Optimum design of triode-like JFET's by two-dimensional computer simulation

A new, planar, surface-grid, field-controlled thyristor (FCT) structure is described. The structure is fabricated by using orientation-dependent (preferential) etching and selective vapor epitaxial growth to obtain vertical grid walls. The resulting high channel-length-to-width aspect ratio produces devices with high blocking gains and fast gate turnoff speeds. Devices have been fabricated with the capability of blocking more than 1000 V with an applied grid bias of 32 V, and simultaneously exhibiting a low forward voltage drop in the on-state. These surface-grid devices exhibit gate turnoff capability with turnoff times of less than 500 ns at a rated cathode-anode current of 1 A.

Vertical channel field-controlled thyristors with high gain and fast switching speeds

Semiconductor power devices are designed to rapidly switch or amplify high currents, to support high voltages, and to control electric power. Because of these requirements, their topographies and structures are different from those of small-signal devices. Specific designs are the result of the understanding of the physics of p-n junction HV breakdown, gain variation at high currents, current instabilities, etc. After introducing elementary semiconductor structures, the author reviews the basic principles of the operation of bipolar and field-effect power transistors and thyristors. This is followed by a discussion of phenomena of special interest for power devices; junction avalanche breakdown, the effect of the current level on the current gain, dynamic and static behaviour at high currents and thermal properties and instabilities. The review includes recent advances in device physics and introduces the reader to new methods of improving device performance. Power is a relative concept-at microwave frequencies at few watts is a very large quantity; this review therefore includes a section on microwave power devices.

https://iopscience.iop.org/article/10.1088/0034-4885/45/4/002/pdf

Physics of semiconductor power devices

The experimental electrical properties of a vertical channel JFET fabricated by a double diffusion technique are presented. A table showing its principal characteristics for different values of the diffusion depths is included. The analysis of the “triode-like” operation revealed by the output characteristics is based on a two-dimensional numerical simulation of the device. At high drain currents ID is proportional to VDSα (α<1). This behaviour can be attributed mainly to the effect of channel length modulation by the drain voltage. At low drain currents, the potential barrier between the source and the drain determines the current magnitude. This is an exponential function of the barrier height which increases almost linearly when VGS increases and decreases non-linearly when VDS increases.

Entirely diffused vertical channel jfet: theory and experiment

Silicon carbide static induction transistors

Triode-like operation of junction gate FET's is analyzed by two-dimensional computer simulation. Triode-like characteristics are shown to appear with the channel normally off and the depletion layer reaching the drain electrode. Triode-like current arises from carrier injection from the source electrode into the depleted region. Triode-like operation is achieved without intrinsic material.

H. Kodera

Papers

Two-dimensional analysis of triode-like operation of junction gate FET's