Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 12: HL Poster I

HL 12.63: Poster

Montag, 1. April 2019, 17:30–20:00, Poster E

Temperature dependent electrical characteristics of a junction field effect transistor for cryogenic sub-attoampere charge detection — •Hüseyin Azazoglu, Paul Graf, Anahita Kavangary, Meike Flebbe, Kornelia Huba, Hermann Nienhaus, and Rolf Möller — Fakultät für Physik/Cenide, Universität Duisburg-Essen, Germany

The electrical input and output characteristics of a commercial n-channel junction field effect transistor (JFET) is studied as a function of temperature in the range between 30 and 300K. As long as the charge carrier concentration is constant an increasing drain current is observed for reduced temperatures and low gate voltages. Using a constant mobility model for the device this behaviour can be explained with the higher electron mobility in the source-drain channel. For larger negative gate voltages a source-drain voltage is found at which the drain current is almost temperature independent. As soon as the charge carriers freeze out the input characteristics changes significantly due to the exponential decrease of the carrier concentration. The source-gate leakage current is measured through the entire temperature range in an open gate configuration. It decreases exponentially with lower temperatures by more than six orders of magnitude and reaches values of 0.01 attoampere below 160K. The result can be explained by the generation of electron-hole pairs in the depletion layer in agreement with the Shockley-Read-Hall model. As a consequence, JFETs at cryogenic temperatures can be employed as almost perfect charge detectors. Applications, e.g. in scanning probe potentiometry, are discussed.