Laser annealing study of the grain size effect in polycrystalline silicon Schottky diodes

Laser annealing is used to controllably vary the grain size of polycrystalline silicon films. The properties of Schottky diodes formed in such layers are studied experimentally by I-V and C-V measurements and interpreted in the framework of the grain boundary trapping model for polycrystalline silicon. For large grained material (grain size ≊10 μm) nearly ideal Schottky diode characteristics with a diode factor n close to unity are found. As deposited, fine grained material is fully depleted at the doping levels employed and yields a p-i-n diode behavior characterized by n=2. Observation of this regime without series resistance limitations is possible by using a buried n⁺ layer as the back contact of the diodes. Reverse currents of the diodes are inversely proportional to the grain size, as expected for generation at grain boundary traps.