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HL: Fachverband Halbleiterphysik

HL 75: Poster IIIB

HL 75.7: Poster

Donnerstag, 19. März 2020, 15:00–17:30, P2/3OG

Open-gate junction field effect transistors as cryogenic charge detectors with attoampere leakage — •Tom Risse, Hüseyin Azazoglu, Kornelia Huba, Hermann Nienhaus, and Rolf Möller — Faculty of Physics/Cenide, University of Duisburg-Essen, Germany

Open-gate junction field effect transistors (JFET) at cryogenic temperatures can be employed as almost perfect charge detectors with leakage currents of less than 0.1 aA [1]. The minimum detectable charge is primarily determined by the leakage current between the source and gate terminals. The intrinsic leakage current is due to a generation of charge carriers in the pn-depletion zone and may be well described by the Shockley-Reed-Hall model. The extrinsic leakage current occurs through parasitic resistive current paths outside the JFET, e.g. due to contaminations. Both contributions can be precisely distinguished by measuring the variation of a gate discharge current with time. The study reports on the intrisic leakage current in the JFET BF545B at 220 K and at room temperature. By reducing the parasitic resistances a leakage current of 2.1 aA is achieved and charges of only 14 aC can be determined. The gate contact of the cryogenic device is successfully connected to an external electrode which allows sensitive charge detection in setups at room temperature. Examples of low charge detection due to UV- , alpha- and beta radiation as well as of detection of moving charged droplets by electrostatic induction are demonstrated. [1] A. Kavangary et al. AIP Advances 9, 025104 (2019).