Thermal detector based on a suspended polyimide membrane for infrared radiation applications

This Letter details a pioneering study on the design and nanofabrication process of a thermoelectric infrared radiation detector using a suspended polyimide membrane. The research includes a comprehensive analysis of thermoelectric doped Bi2Te3 thin films, comparing their expected performance regarding noise and specific detectivity with other infrared detectors, particularly those in the silicon sector. Experimental results and calculations shed light on responsivity and time constants. In the absence of absorption layers, specific detectivity values for visible and near infrared radiation are measured at 9.2 × 107 and 2.9 × 107cm Hz/W, respectively, with a time constant nearing 20 ms. Calculations show that introducing an optimized absorption layer with ε = 1 significantly improves specific detectivity, reaching 9.0 × 108cm Hz/W. Subsequent calculations also show that further enhancement can be obtained by etching the polyimide membrane to a 1-micron thickness, resulting in an exceptional specific detectivity value of 8.4 × 109cm Hz/W, placing it among the best in the current state-of-the-art.