Detection of Electronic Defects in Strip-Heater Crystallized Silicon Thin Films

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Abstract
Electronic defects in strip-heater crystallized silicon thin films have been investigated with capacitance-voltage (C-V),deep-level spectroscopic, and scanning-electron microscopic techniques. For electrical characterization the crystallized silicon films were used to fabricate inverted metal-oxide-silicon capacitors in which degenerately doped bulk silicon substrates provided the gate electrode. High-frequency C-V characteristics yield effective fixed-charge densities in the oxide of ≤ 2×1011 cm−2. Trap-emission spectra, recorded with deep-level transient spectroscopy on both p-type and n-type capacitors, indicate a continuous distribution of deep levels throughout the silicon bandgap. The Si-SiO2 interface is considered to be the principal source of this deep-level continuum, since the films are essentially single crystal with a low density of subgrain boundaries; the effective interface-state density is ≤ 2.5×1010 eV−1 cm−2. A discrete energy level, detectable above the background continuum,appears in the upper half of the silicon bandgap; it may identify a point defect in the bulk of the silicon film with a spatially uniform density of approximately 1×1013 cm−3. On lateral p-n junction diodes, electron-beam-induced-current images reveal enhanced diffusion of arsenic along structural defects intersecting the junction.