Electrical Properties of High‐Purity Silicon Made from Silicon Tetraiodide

Abstract

Resistivities, type of conduction, and lifetimes of minority carriers of single crystals of iodide silicon are recorded as a function of the purification procedure for silicon tetraiodide. Samples of silicon have been prepared by decomposition of silicon tetraiodide on hot tantalum and hot quartz surfaces in vacuum. Distillation in a 12 plate quartz column of silicon tetraiodide prepared from 99.7% silicon results in single crystals of silicon that are uniformly n‐type with maximum resistivities at the seed end in the range 0.3–1 ohm‐cm. Two recrystallizations from solvents before the distillation step result in both p‐ and n‐type crystals with, respectively, 150–650 ohm‐cm and 75–170 ohm‐cm resistivity ranges at the seed ends. Distillation of silicon tetraiodide is particularly effective in removing boron, while recrystallization and zone melting are effective for removing group V impurity iodides.