On approaches to the built-in electric-field calculations in shallow silicon n+-p junctions

A critical appraisal of recent approaches to the built-in electric-field E calculations in shallow heavily doped strongly asymmetric silicon n⁺-p junctions is performed. The existence of a large (≃ 1 - V/µm), positive field E of built-in nature on the surface of the n⁺-layer-reported previously through the computation of E as a gradient of erfc impurity profile in very steep n⁺-p junctions-is refuted on the grounds of semiconductor fundamentals. Alternatively, it is shown that: 1) under thermal equilibrium conditions and a "free" (air or vacuum) silicon surface, the built-in field should necessarily go to zero at the semiconductor surface; 2) if the projected built-in field E nears the surface on the heavily doped side of a junction, then it is compulsory to take into account the interaction between E and the prevailing surface charges. The results of this work suggest that all processes in the surface-controlled region of the heavily doped layer are being shaped by the interplay of the bulk field E created by the impurity gradients with the field Esurforiginated in the surface states.