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) × 10 17 electrons/cm 2 with a mean current density of 8.1 A/cm 2 in a Van de Graaff accelerator at 100 °C in a N 2 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 kickout mechanisms were identified for substitution of migrating atoms in the GaAs substrate.

Diodes Fabricated by Electron Beam Doping (Superdiffusion)Technique in Semiconductors at Room Temperature

“…In experiments of the GaAs/Si(Zn)//Si(Zn)/GaAs system, the photoluminescence Si(Zn) peaks confirmed the occurrence of the neutral acceptor-bound exciton (A 0 , X) [27]. Electron irradiation also produces high concentrations of electron-hole pairs in Si.…”

“…These processes are described in detail below. The production rate of Frenkel defects ( ) in Si for 750 keV electrons is approximately 1.24 cm 1 [23], and the concentration of Frenkel defects introduced at an electron fluence of 5 10 17 electrons/cm 2 is 3 10 16 cm 3 [27] N sii = N SiV , where N sii and N siV are the concentrations of Si interstitials and vacancies, respectively. If 10% of the vacancies recombine with the interstitials in Frenkel defects in the bulk, a certain concentration (90%) will remain as interstitials in the crystal [27].…”

“…The production rate of Frenkel defects ( ) in Si for 750 keV electrons is approximately 1.24 cm 1 [23], and the concentration of Frenkel defects introduced at an electron fluence of 5 10 17 electrons/cm 2 is 3 10 16 cm 3 [27] N sii = N SiV , where N sii and N siV are the concentrations of Si interstitials and vacancies, respectively. If 10% of the vacancies recombine with the interstitials in Frenkel defects in the bulk, a certain concentration (90%) will remain as interstitials in the crystal [27]. As these displaced atoms lose energy along the migration path [24] and the migration energy of interstitials is very small (0 0.22 eV) [25], the displaced atoms will become fixed at or near the interface.…”

“…7 %) for substrate No.3, the P and Si atoms are more effectively doped in comparison with the n-type Si and n-type GaAs substrates (eff. 0.1-0.8 %), respectively [27]. Superdiffusion processes and the kick-out mechanism can be expected to be enhanced by the hole carriers in the p-type wafers.…”

“…The effects[27] of modified EBD for P and B doping in Si//P//Si (p-type, substrate No.1), and Si//B 6 Si//Si (n-type, substrate No.2), Si and Zn doping in GaAs/Si//Si/GaAs (p-type, substrate No.3), GaAs/Zn//Zn/GaAs (n-type, substrate No.4) and GaAs/Si//Si/GaAs (undoped, substrate No.5) were reported.…”