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

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-likeI-Vcharacteristics. Triode-like characteristics depend strongly on device geometry. This operation can be realized only in short gate devices. The channel thicknessais 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 lgdis also essential in determining breakdown voltage. The design criteria are discussed and an optimum design specified on the ND(channel doping)-aandN_{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.