Performance of GaAs microbridge thermocouple infrared detectors

GaAs microbridge thermocouples with lengths ranging from 40 to 650 mu m and operating at room temperature have been fabricated for the detection of infrared radiation. A CO2 laser of a 10.6-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 x 10(6) cm Hz(1/2)/W and a time constant of 2.2 ms have been measured in vacuum for 650-mu m-long bridges, and a shorter time constant of 50 mu s was obtained for 40-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. [203]