Hot-wire CVD poly-silicon films for thin film devices

Solar cell using profiled poly-Si:H by HWCVD as i-layer in the configuration SS/n-mu c-Si:H(PECVD)/i-poly-Si:H(HWCVD)/p-mu c-Si:H showed 3.7% efficiency. A current of 23.6 mA/cm(2) was generated in only 1.5 mu m thick poly-Si:H i-layer grown at similar to 5 Angstrom/s. TFTs made with the poly-Si:H films (grown at greater than or equal to 9 Angstrom/s) exhibited remarkable stability to long duration of 23 hours of gate bias stress of similar to 1MV/cm. A saturation mobility of 1.5 cm(2)/Vs for the TFT has been achieved. Films made at low hydrogen dilution (Poly2) showed device quality (purely intrinsic nature, ambipolar diffusion length of 568 nm, only (220) oriented growth and low ESR defect density of <10(17)/cm(3) with complete absence of signal due to conduction electrons) but with an incubation phase of amorphous initial growth, whereas the films made at high hydrogen dilution (Poly1) had a polycrystalline initial growth, though with higher defect density, incorporated oxygen and randomly oriented grains. Poly2 films are compact and hydrogen bonding is at compact Si-H sites manifested as 2000 cm(-1) IR vibration and high temperature hydrogen evolution peak. Exchange interaction of spins and spin pairing are observed while increasing defects in such a compact structure. A new approach has been used to integrate these two regimes of growth to make profiled poly-Si:H layers. The new layers show good electronic properties as well as complete elimination of incubation phase.