Characteristics of [115] Dislocation-Free Silicon Crystals

Dislocation-free silicon crystals with [115] crystallographic orientation were grown by the float-zone method. The relatively high (115) surface free energy allows more uniform growth, particularly for dopant incorporation, than that which is characteristic of low surface free energy planes such as (Iii). The macroradial variation of resistivity in phosphorus-doped [115] crystals is typically less than 5%. Also, low surface-state charge densities can be achieved using low oxygen content [115] float-zoned crystals. (100) wafers, circular within 4%, may be cut from these crystals. The major i ty of float-zoned silicoR crystals for semi-conductor use have historical ly been grown in <111> orientations. This was favorable for early alloy junc-tion devices since the {111} planes tended to define a sharp junction boundary. In the early 1960's, crystal suppliers attempted <100> crystal zoning and wer