Performance of GaAs microbridge thermocouple infrared detectors

GaAs microbridge thermocouples with lengths ranging from 40 to 650 μm and operating at room temperature have been fabricated for the detection of infrared radiation. A CO ₂ laser of a 10.6-μm wavelength was used to characterize the performance of the detectors in air and in vacuum. A responsivity of 4.2 V/W with a corresponding detectivity D* = 8 × 10 ⁶ cm Hz ^1/2/W and a time constant of 2.2 ms have been measured in vacuum for 650-μm-long bridges, and a shorter time constant of 50 μs was obtained for 40-μm-long bridges. An analytic thermal transport model has been used to simulate the operation of the sensors. The heat-transfer coefficient has been evaluated by comparing the data from air and vacuum measurements. The spectral response and the absorbance of the microbridge have also been presented.