Evaluation of 1/f noise in prospective IR imaging thin films

Vanadium oxide (VO_x) and hydrogenated silicon germanium (Si _xGe_1-x) are the two predominant thin film material systems used as the active layer in resistive infrared imaging. Thin films of VOx used in microbolometers have a resistivity typically between 0.1 and 1 Ω-cm with a temperature coefficient of resistance, |TCR| between 1.4%/K to 2.4%/K, while Si_xGe_1-x:H thin films have a resistivity between 200-4,000 Ω-cm with a |TCR| between 2.9%/K to 3.9%/K. Future devices may require higher TCR materials, however, higher TCR is loosely associated with higher resistivity and therefore also with high noise. This work compares 1/f noise of high resistivity VO_xand Ge:H thin films having |TCR| < 3.6%/K. The high TCR thin films of VO_xwere found to be amorphous while, depending on the deposition conditions, the Ge:H thin films were either amorphous or mixed phase of amorphous + nanocrystalline. Evaluation of these VO_x and Ge:H thin films indicates a prospects for a superior process-property relation of 1/f noise in Ge:H thin films in comparison with thin films of VO_x.