Oxygen and erbium distribution in diffusion doped silicon

Abstract

Silicon doped with rare-earth metal erbium is a promising material for the fabrication of highly efficient light emitting structures that can be easily integrated into silicon electronics. The fabrication technology of these structures includes little if any diffusion processes because the efficiency of erbium luminescence in diffusion structures is low. It is still unclear what causes this low erbium luminescence efficiency: low impurity concentration, low optical activity of the luminescence centers or luminescence extinction by the defects. The composition of diffusion silicon layers doped by rare earth erbium has been investigated. The diffusion source was an erbium oxide layer on the surface of the test silicon wafer. The erbium and oxygen distribution profiles in silicon have been measured by SIMS. The concentration of electrically active erbium impurity in the diffusion layers on silicon has been determined by measuring the surface resistance and carrier mobility during consecutive etching of layers. The erbium diffusion coefficient at 1240°C has been estimated to be 4.8·10–13cm2·s−1. The concentrations of electrically active (8·1016cm−3) and total (3·1018cm−3) erbium in the surface silicon diffusion layers prove to differ noticeably in the presence of high oxygen concentration (>1019cm−3). A model of erbium and oxygen simultaneous diffusion has been suggested. The model takes into account the association of erbium and oxygen into complexes. The results of numerical simulation and experimental data are in a good agreement for the near-surface region of the diffusion layer.