DESIGN OF AN N-CHANNEL JFET ON HIGH-RESISTIVITY SILICON FOR RADIATION-DETECTOR ON-CHIP FRONT-END ELECTRONICS

We report on the design of an n-channel Junction Field Effect Transist or (JFET) on fully-depleted, high-resistivity (5 k Omega cm), n-type s ilicon substrate, which is intended to be utilized as an active device in the on-chip preamplifier of the silicon radiation detectors we are developing. Two-dimensional process and device simulations are employ ed to optimize the device doping profile, as well as to point out some important advantages of the proposed structure over possible alternat ive device designs. In particular, the proposed JFET, in which an exte rnally-contacted, p-type well isolates the active device from the high -resistivity substrate, presents higher output-resistance values than a device directly fabricated on substrate. Moreover, it is not affecte d by a parasitic phenomenon resulting in gate-current increase and noi se-performance degradation, which, in contrast, characterizes a device with a floating well.