Performance of GaAs microbridge thermocouple infrared detectors

GaAs microbridge thermocouples with lengths ranging from 40 to 650 /spl mu/m and operating at room temperature have been fabricated for the detection of infrared radiation. A CO/sub 2/ laser of a 10.6 /spl mu/m 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/spl times/10/sup 6/ cm Hz/sup 1/2//W and a time constant of 2.2 ms have been measured in vacuum for 650-/spl mu/m-long bridges, and a shorter time constant of 50 /spl mu/s was obtained for 40-/spl mu/m-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.