J. Phys. IV France 08 (1998) Pr3-123-Pr3-126
Development of cryogenic Ge JFETsR.R. Ward1, R.K. Kirschman1, 2, M.D. Jhabvala3, R.S. Babu4, N.C. Das5, D.V. Camin6 and G. Pessina6
1 Germanium Power Devices Corp., 300 Brickstone Square, York Street, Box 3065, Shawsheen Village Station, Andover MA 01810-3065, U.S.A
2 Consulting Physicist, Mountain View, P.O. Box 391716, Mountain View CA 94039, U.S.A
3 NASA Goddard Space Flight Center, Greenbelt, Maryland, U.S.A.
4 Ball Aerospace and Technologies Corp., Boulder, Colorado, U.S.A.
5 Hughes/STX, Lanham, Maryland, U.S.A.
6 Physics Department of the University and INFN, Dipartimento di Fisica dell'Università and Istituto Nazionale di Fisica Nucleare, INFN, Via Celoria 76, 20133 Milano, Italy
We report on initial development of new Ge JFETs for deep cryogenic (liquid-helium range) operation. Both p- and n-channel Ge JFETs were fabricated. Due to unsatisfactory epitaxial growth, the p-channel JFETs do not exhibit usable characteristics. The n-channel Ge JFETS have good dc characteristics at room temperature, 77 K and 4 K, although at 4 K they exhibit a threshold and "steps" as also observed in earlier Ge JFETs made by Texas Instruments. Noise measurements at 4 K with Vds = 1.2 V and Id = 0.3 mA give en of ≈ 0.5-1 µV/Hz1/2 at 1 Hz and ≈ 20-30 nV/Hz1/2 at 10 kHz (input referred). This is considerably higher than that of the best Si JFETs operating at higher temperature or the best GaAs MESFETs operating at 4 K. However, we believe that with refinement of the design and fabrication the noise of the Ge JFETs can be reduced to a range suitable for deep cryogenic applications.
© EDP Sciences 1998