Phosphorus-doped polycrystalline silicon is grown in an epitaxial reactor by the reduction of a hydrogen-diluted silane-phosphine mixture passing over a substrate heated to 800°C. The influence of the phosphine-silane ratio on growth rate, electrical resistivity, active donor concentration, and Hall mobility is examined. It is found that phosphine inhibits growth rate at 800°C to a lesser degree than it does at lower growth temperatures. Growth rate progressively drops to 0.6 of the undoped value as the phosphine-silane ratio is increased to 10 ^-1 . Resistivity drops from 1 to 10 ^-3 Ω. cm as active phosphorus concentration varies between 10 ¹⁸ and 4 × 10 ²⁰ cm ^-3 , while Hall mobility rises from 4 to 30 cm ² / V.s. Diodes are formed between the grown polysilicon layers and the single-crystal p-type silicon substrates. They are found to have recombination currents critically dependent on the phosphine/ silane ratio during growth of the polysilicon. As this ratio increases above 10 ^-5 , recombination decreases, while mobility in the polysilicon increases. These results support the "dopant segregation" theory of conduction in polysilicon. For ratios of 10 ^-3 to 10 ^-2 the diodes obtained showed a recombination factor approaching those of diffused diodes and are useful devices, for example, as the emitter-base junction of a shallow-base high-frequency, bipolar transistor.

Z. Lieblich

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