2:00 PM - 2:15 PM
▲ [19p-A402-3] Study on NEP for optimization of THz Antenna-Coupled Ti Microbolometers with Straight and Meander Shaped Thermistors
Keywords:Antenna-Coupled Microbolometer, Meander Thermistor, Noise Equivalent Power
Room-temperature antenna-coupled Ti microbolometers with straight wire shaped thermistors (lengths - 25, 50, 10 µm and width - 0.2 µm) and meander shaped thermistors (length - 48.7 µm and width - 0.2 µm heater length – 11.2 µm) were fabricated and analyzed. Sensitivity is one of the important parameter for optimizing the microbolometer characteristics, which can be analyzed in terms of noise equivalent power (NEP). To estimate the NEP, voltage noise was measured for the microbolometers with the use of dynamic signal analyzer over a frequency range of 10 kHz -10 Hz. To enhance the bolometer performance maximum allowable bias current was applied at the thermistors. The measured spectra exhibits both frequency and bias current dependence. The bias current dependence can be clearly seen as the noise voltage gradually increases with the increased bias current. Fig.2 (b) represents the dependence of voltage noise and bias current on lengths of the thermistor. Since the noise voltage is direct proportional of resistance, the longest bolometer shows large noise voltage than others, though its applied bias current is small. Trade-off existing between NEP and responsivity (Rv) .
NEP was estimated from the measured noise voltage at 100 Hz and responsivity under same bias current. For the straight wire thermistors the minimum NEP of 5.91 x 10-11 was obtained for the longest device (length - 100 µm) which has the largest responsivity of 976 V/W. Similarly, for meander shaped bolometer which has the responsivity of 286.4 V/W, the calculated NEP is 1.75 x 10-10 . Even though, the length of the meander thermistor is large, due to its structure it is possible to reduce the entire bolometer length. By narrowing the thermistor width and increasing the length of meander thermistor can be a promising detector for antenna-coupled bolometers.
NEP was estimated from the measured noise voltage at 100 Hz and responsivity under same bias current. For the straight wire thermistors the minimum NEP of 5.91 x 10-11 was obtained for the longest device (length - 100 µm) which has the largest responsivity of 976 V/W. Similarly, for meander shaped bolometer which has the responsivity of 286.4 V/W, the calculated NEP is 1.75 x 10-10 . Even though, the length of the meander thermistor is large, due to its structure it is possible to reduce the entire bolometer length. By narrowing the thermistor width and increasing the length of meander thermistor can be a promising detector for antenna-coupled bolometers.