Detection mechanisms in microstrip dipole antenna-coupled infrared detectors

We compare the detection mechanisms employed in microstrip dipole antenna-coupled infrared detectors. The electrical currents induced along the antenna arms are detected by a rectangular niobium. (Nb) microsensor placed at the center of the antenna. The ohmic nature of the Au-Nb contact determines the detection mechanism. Devices with linear contacts between the Au antenna arms and the Nb microsensor exhibit bolometric response. A nonlinear Au-insulator-Nb junction rectifies the induced antenna currents. Devices with nonlinear contacts also exhibit a bolometric response. The devices with nonlinear contacts are 1/f noise limited while the devices with linear contacts are Johnson noise limited. The rectification mechanism is 5.3 times faster than the thermal detection. The current-voltage (I-V) characteristic of the devices exhibiting bolometric response is linear, while that of the rectifying devices is cubic. For devices with nonlinear contacts excellent agreement is obtained between the measured detector response and the ratio between the second and the first derivative of the I-V characteristic. (C) 2003 Elsevier Science B.V. All rights reserved.