5 March 2003 Development of Ge JFETs for deep-cryogenic preamplifiers
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Cooled detectors for IR, visible, UV and X-rays often require a preamplifier that can operate at deep cryogenic temperature, down to the liquid-helium range. Preamplifiers based on available silicon or gallium arsenide transistors have not been entirely satisfactory. With this in mind, we have been developing junction field-effect transistors (JFETs) based on germanium. Our objective has been to achieve stable dc characteristics and very low noise down to as low a cryogenic as possible. We have obtained good dc characteristics down to liquid-helium temperature and low noise down to ≈30 K with Ge JEFTs. Between approximately 30 and 80 K, low-frequency gate-referred noise voltage is ≈30-60 nV/rtHz at 1 Hz, decreasing to <2 nV/rtHz above ≈1 kHz for 40 μm by 1560 μm gate n-channel Ge JFETs with drain current of 330 μA and dissipating approximately 400 μW. For lower and higher drain current the "1/f" noise remains approximately the same, but the white noise increases or decreases as expected. We are continuing development with the goal of extending the same low noise characteristics down to 4K.
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Rufus R. Ward, Rufus R. Ward, Randall K. Kirschman, Randall K. Kirschman, Murzy D. Jhabvala, Murzy D. Jhabvala, R. Sachidananda Babu, R. Sachidananda Babu, David V. Camin, David V. Camin, Valerio Grassi, Valerio Grassi, "Development of Ge JFETs for deep-cryogenic preamplifiers", Proc. SPIE 4850, IR Space Telescopes and Instruments, (5 March 2003); doi: 10.1117/12.461756; https://doi.org/10.1117/12.461756

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