1/f noise in a-Si1-xCx:H thin films as novel thermistor materials for micro-machined IR sensors

A superior infrared (IR) sensor of D* = 8.0 x 10(8) cm Hz(1/2)/W with a micro-machined structure has been successfully fabricated. An increase in sensitivity was realized by using a boron doped hydrogenated amorphous silicon carbide (a-Si1-xCx:H) film with an activation energy, E-a, and also reducing its noise. Structural uniformity and carrier density were changed by controlling deposition parameters. The 1/f noise (flicker noise) was reduced by decreasing the amount of Si-CH3 and C-H-n bonds in the a-Si1-xCx:H. Though the doping increased the structural disorder, the 1/f noise was also reduced as the doping level increased. We conclude that the 1/f noise does not originate from the structural disorder nor neutral dangling bonds which act as recombination centers, but from the structural non-uniformity causing fluctuations of the carrier conduction. Comparing films with the same E-a at different doping levels and CH4/SiH4 ratio, heavily doped films show lower 1/f noise. (C) 1998 Elsevier Science B.V. All rights reserved.