Impurity lattice location and recovery of structural defects in semiconductors studied by emission channeling

Abstract

Doping of semiconductors by ion implantation usually requires implantation doses below 10¹³ cm⁻² to obtain typical impurity concentrations of <10¹⁸ cm⁻³. The lattice location of impurities as well as the defect recovery after such low dose implantations can be studied using the emission channeling technique. In this technique, single crystals are doped with radioactive probe atoms and the channeling effects of electrons, positrons or α-particles emitted from these atoms are measured. We present a quantitative analysis of electron emission channeling measurements after heavy-ion implantation into Si and III–V compound semiconductors by comparison with calculated channeling profiles based on the dynamical theory of electron diffraction. For In atoms implanted into Si, complete substitutionality was found after rapid thermal annealing to 1200 K. For lower annealing temperatures, the observed channeling effects indicate small mean displacements (of about 0.2 Å) of the In atoms from substitutional sites, caused by residual implantation defects. For GaAs, GaP and InP implanted at low temperatures with In or Cd isotopes, pronounced recovery stages around 300, 400 and 350 K, respectively, were observed and substitutional fractions close to 100% were derived after annealing above the stage.