Potential of Ti doped hydrogenated amorphous Si film with suitable resistivity and high TCR for microbolometer applications

In order to acquire good sensitive amorphous silicon film used for thermal-image infrared detector, different concentrations of titanium-doped hydrogenated amorphous silicon were prepared by magnetron sputtering. To assess how composition and structure affect their electrical characteristics, RBS (Rutherford Back Scattering), Raman, transmission spectrum and temperature dependence on conductivity are measured. It clearly shows that adding Ti atoms to amorphous silicon tends to decrease both the resistivity and temperature coefficient of resistance (TCR). The decreasing TCR value with Ti content is mainly attributed to the decrease of the activation energy and bandgap. However, a kink of conductivity and TCR is observed in undoped a-Si:H and Ti doped a-Si:H with Ti content of 3% in different temperature range, while constant TCR is found in higher Ti doped a-Si: H with Ti content larger than 3%. Possible mechanism is discussed. Using the M value (TCR/ρ1/2), the optimum sample is supposed to be Ti content of 3.5% with TCR −1.134%/K and resistivity 47 Ω cm.