DYNAMIC AND NOISE PERFORMANCE OF LARGE GATE AREA MESFETS MADE IN A MONOLITHIC PROCESS

Metal-Semiconductor Field Effect Transistors (MESFETs) with gate area up to 48000 mum2 have been designed and fabricated using an ion-implanted GaAs monolithic process. They have been characterized at 300 K and in particular at 77 K and 4 K as they will be used at the input stage of low-noise preamplifiers for different kinds of cryogenic particle detectors. A single device with W = 6000 mum has a l/f noise sufficiently low to substitute it for a group of ten discrete MESFETs of the best quality put in parallel at the input of voltage-sensitive preamplifiers for bolometric detectors. A substantial reduction of noise, with high speed and low power dissipation was obtained in a prototype of a preamplifier designed for LAr calorimetry. Using the SPICE parameters extracted from measurements done on the present FETs, we have designed monolithic low noise preamplifiers for the mentioned applications. The chips are presently under fabrication.