Superdiffusion of impurity atoms in damage‐free regions of semiconductors

Abstract

The effect of the elegant superdiffusion process was examined in the unirradiated region for three layer structures. GaAs semiconductor substrates coated with vacuum-evaporated Si were doped with Si by electron beam doping (EBD) at 750 keV using GaAs/Si//Si/GaAs systems. The samples were exposed to an electron beam with a fluence of (3.7–5.0) × 1017 electrons/cm2 with a mean current density of 8.1 A/cm2 in a Van de Graaff accelerator at 100 °C in a N2 gas atmosphere. The irradiated samples were inspected by secondary-ion mass spectrometry and photoluminescence analysis, revealing the occurrence of superdiffusion. It was found that EBD occurs as a result of the interstitial migration of displaced interstitial atoms toward the Si//Si interface, strong surface diffusion at the interface, and high impurity concentrations at the interface that induce concentration- and recombination-enhanced diffusion. Two kick-out mechanisms were identified for substitution of migrating atoms in the GaAs substrate.