Research On Metal-doped Amorphous Silicon Thin Film And Its Device Application

Having many special advantages of electric conductivity, low energy consumption, and easy for integration, semiconductor devices are widely used in energy, communication, medical, military industry and so on. In the family of semiconductor devices, most of them are made of silicon or silicon-related materials. With the continuous development of information technology and the improvement of fabrication processes, a wide variety of silicon-based devices with different performance have been developed.In this thesis, amorphous silicon ruthenium(a-Si1-xRux) alloy films are fabricated. Ru atoms are introduced into the films by radio-frequency co-sputtering, and the influence of Ru on the structural, optical and electrical properties of both as-deposited and annealed films is deeply studied. Results indicate that the increase of nominal concentration of Ru atoms in a-Si1-xRux thin films would further degrade the short-range order of amorphous network. However, reasonable Ru alloying would narrow the optical band gap and lower the defects of amorphous silicon film. At the same time, the Si-Si bonding becomes more stable while the films become more compacted. In addition, the film conductivity develops sharply with the increase of Ru concentration, and the conductivity of a-Si1-xRux film with 8 % concentration of Ru is up to 0.1 S/cm. The temperature coefficient of resistivity(TCR) of the alloyed films decreases with the increase of Ru concentration amount, but can remain above 2 % with an appropriate concentration. The results indicate that a-Si1-xRux thin film bas a better conductivity with an appropriate TCR, which might make the film a promising application in infrared detectors.Amorphous silicon-silver(a-Si1-xAgx) alloy films are also fabricated by RF co-sputtering technology. The microstructure and optical performance of a-Si1-xAgx films with different Ag alloying concentration have been investigated. A sandwich structure consisting of a top metal(Ag) electrode, an active a-Si layer and a heavily doped p-type crystalline silicon(p-Si) as the bottom electrode, is designed and fabricated so that the resistance switching behavior of a-Si based memristor can be studied by in-situ ellipsometry. Moreover, the a-Si1-xAgx film is combined with a silicon-based optical waveguide to form a new integrated photonic switching device, and the light switching behavior of this novel a-Si/Si-waveguide has been investigated by means of a simulation software. When the optical switch is “on” resulting from Ag filament forming into the a-Si film, the incident light propagates in the waveguide smoothly. But when the optical switch turns “off” resulting from Ag filament escaping back to the Ag electrode, the energy of light in waveguide is coupled into the a-Si layer and then absorbed effectively. The simulation result also shows that this novel optical switch has a great extinction ratio in “off” state, and the insertion loss is very small.