Semiconductor Properties of Recrystallized Silicon in Aluminum Alloy Junction Diodes

Abstract

This is a study of the basic electrical properties of thin recrystallized regions formed in the fabrication of PN junctions by the alloying of pure aluminum on N‐type silicon single crystals. The average aluminum concentration is about 7×10¹⁸ cm⁻³, and varies by a factor of 4 to 5; being largest in the region first recrystallized and decreasing in a linear manner to the surface immediately beneath the aluminum‐silicon eutectic. The average Hall‐hole mobility is about 55 cm² volt⁻¹ sec⁻¹ and varies from 35 to 75 cm² volt⁻¹ sec⁻¹ across a region formed by precipating from 977°C to the eutectic. Across the same region the conductivity varies from 72 to 35 mho cm⁻¹. The built‐in field which is both a function of depth and total width can vary from 10 to 200 v per cm in typical cases. The minority carrier (electron) diffusion length ranges from 4 to 12 μ. The temperature dependence of the distribution coefficient corresponds to an enthalpy change (differential heat of solution) of +0.43 ev necessary for the transfer of an atom of aluminum from the liquid to the solid.