Silicon photodetector integrated on a lithium tantalate substrate

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Abstract
We report the fabrication of metal-oxide-semiconductor field-effect transistors (MOSFET’s) in laser recrystallized silicon films on a lithium tantalate substrate with an intervening silicon dioxide layer. Deposited polycrystalline silicon films were irradiated with a scanning focused argon ion laser beam which caused melting and subsequent crystallization of the silicon film into crystallites suitable for MOSFET fabrication. Melting and recrystallization of the silicon film without damaging the substrate were accomplished by irradiation with 0.3–0.4 W of argon ion laser power focused to a 50-μm-diam spot. Transistor channel mobility was measured to be 50 cm2/Vs. When operated as integrated photodetectors, a responsivity of approximately 0.5 A/W was measured. Theoretical operation of these MOSFET’s as integrated photodetectors is derived and compared to observed operation.