The SuperFET : a high-performance GaAs voltage-controlled current source for cryogenic applications

Abstract
We have developed a monolithic three-terminal voltage-controlled current source which operates between 300 K and 4 K, has large intrinsic voltage amplification and compliance, resembling therefore a high-performance field-effect transistor: the SuperFET. Two additional terminals allow for optional and auxiliary biasing. This structure was fabricated using a GaAs MESFET foundry process that has three types of FETs available with quite different breakdown and threshold voltages. By properly combining three FETs, one of each type, high performance is obtained in the three-terminal structure: the intrinsic voltage amplification at 77 K is at least 10000 for a drain voltage up to 15 V. The input FET has a width of 50000 µm to assure low series noise. Based on the SuperFET configuration, a charge-sensitive preamplifier was implemented for demonstration, using additional circuitry included on the chip. This preamplifier develops output pulses up to 10 V, a value 2.5 times larger than the highest so far reached with cryogenic GaAs monolithic circuits. This opens new interesting opportunities in applications where, besides low noise and high speed, dynamic range is a demanding requirement. One such application is the signal amplification of cryogenic liquid calorimeters used in high-energy physics experiments.