High Responsivity ${\rm a\!-\!Si}_{\rm x}{\rm Ge}_{1-{\rm x}}{\rm O}_{\rm y}:{\rm H}$ Microbolometers

Microbolometers of a-Si
_0.15
Ge
_0.85
O
_.0.236
:H were fabricated by radio frequency (RF) magnetron sputtering. A sandwich layer of silicon nitride-silicon germanium oxide-silicon nitride was used. Surface micromachining was used to fabricate the detectors into a suspended bridge structure. To reduce the 1/f-noise, the detectors were passivated at 250degC in forming gas. A high temperature coefficient of resistance (TCR) of -4.8%/K was obtained at room temperature. Due to observed photo generation below 2.5 mum of wavelength, the responsivity and detectivity measurements were performed with 2.5 mum long pass filter placed in between the infrared light source and detectors. The highest responsivity and detectivity obtained were 1.05times10
⁴
V/W and 8.27times10
⁶
cm-Hz
^1/2
/W from a 40 mum times 40 mum pixel. Lowest thermal conductance obtained was 4times10
^-8
while the response time was 3.44 ms.