Submicron nickel-oxide-gold tunnel diode detectors for rectennas

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Abstract
Integrated circuit technology has been successfully applied to the design and fabrication of submicron metal-oxide-metal (MOM) tunneling diodes for application in far infrared (FIR) rectennas. The MOM diode and a stripline antenna to enhance collection of FIR radiation were integrated on a silicon substrate using state of the art microelectronic technology and were produced simultaneously. A nickel-oxide-gold MOM tunnel diode was made up of a 0.8-μm-wide nickel layer with approximately 22 Å of a nickel-oxide tunnel barrier layer on top crossed by a 0.8-μm-wide gold layer resulting in a junction area of 0.64 μm2 . The antenna consisted of two 0.8-μm-wide and 6.6-μm-long parallel metal conductors, one nickel and the other gold, separated by a gap of 0.8 μm. The dc current-voltage characteristics of the MOM diode showed that the current dependence on voltage was linear about zero bias up to a bias of about 70 mV. Beyond 70 mV, the characteristics were very nonlinear. The average breakdown field was determined to be 6.6×106 V/cm for nickel-oxide film thicknesses ranging from 15 to 39 Å. The current stressing of the MOM diode produced charge trapping within the nickel-oxide layer. The maximum detection of a low level signal (10-mV ac) was determined to be at a dc voltage of 70 mV across the MOM diode using rectifier current sensitivity measurements. The rectified output signal due to a chopped 10.6-μm CO2 laser incident upon the rectenna device was found to increase with dc bias with a maximum value of 1000 nV for a junction bias of 100 mV at room temperature.