Showing papers by "Werner Wesch published in 1992"

Ion implantation in III-V compounds

Abstract: Because of their specific physical properties A III B V compound semiconductors are widely used for the fabrication of special electronic and optoelectronic devices. For a planar technology ion implantation seems to be the most promising doping method for these materials because the conventional diffusion technology is complicated due to the thermal instability of the materials, and the fabrication of epitaxial layers with parameters required for these purposes is connected with high costs. Besides that ion implantation offers the advantages already known from the silicon technology. However, in the compound semiconductors the variety of possible native defects is higher than in the elementary semiconductors, and the influence of the implantation parameters on the kind and concentration of defects produced during ion implantation is much more pronounced in these materials compared to silicon. As a consequence the annealing of damage as well as the electrical activation of the dopants are more complex processes than in silicon, and the choice of the annealing parameters requires information about kind and concentration of defects produced in the materials. The present paper gives a brief review about damage production connected with ion implantation in GaAs, GaP, InP and InAs. The influence of ion mass, ion fluence, dose rate and implantation temperature on the remaining damage is discussed. Additionally, an overview of the use of different annealing methods (conventional, laser and rapid thermal annealing) for the electrical activation of dopants, especially in ion implanted GaAs layers, is given.

Investigation of the amorphization process in ion implanted AIIIBV compounds

Abstract: Various semiconductors (GaAs, GaP, InAs, InP, Ge, Si) were implanted under identical conditions with 200 keV Ar + ions and 300 keV Se + ions at 80 and 300 K over a wide dose range. It is shown that significant differences occur between GaAs and InAs on the one hand and the other materials on the other hand, which cannot be explained by the ionicity of the materials. The high mobility of Frenkel defects seems to be responsible for the substantial influence of defect annealing and transformation in the arsenides, whereas in the other materials a higher stability of the primarily produced defect clusters can be assumed.

Analysis of defects in weakly damaged GaAs by Monte Carlo channeling simulation

Abstract: Channeling spectra measured at 125 and 295 K for 〈100〉 GaAs single crystals implanted with low dose N ions were analyzed by two methods: analytical dechanneling theory and Monte Carlo computer simulation. From the temperature dependence of dechanneling it was found that the defect structure consists of atoms statically displaced by a given distance from their lattice site position. The role of thermal vibrations of displaced atoms was also discussed.

Differences in the damage production of proton implanted GaAs, Ge and Si investigated by temperature dependent dechanneling

Abstract: 〈111〉-GaAs, Ge and Si wafers were implanted with 60 keV H+-ions at room temperature (Ni= 1 × 1016−8 × 1016 cm−2). Weakly and strongly damaged layers were produced in the different semiconductor materials. Energy and temperature dependent RBS-channeling measurements showed the existence of uncorrelated displaced lattice atoms (point defects or point defect complexes) characterized by different displacement distances ra for GaAs and randomly distributed distances (or large distances) for Ge and Si. The obtained different defect distributions were compared and discussed for the three materials.

Nucleation of point defects in low-fluence ion-implanted GaAs and GaP

Abstract: The defect production due to low-fluence medium-mass ion implantation into GaAs and GaP at room temperature is investigated. In the parameter region analysed weakly damaged layers are created containing point defects and point defect complexes. Temperature dependent channeling measurements show different structures of the damage produced in the two materials. The depth profiles of the near-edge optical absorption coefficient K sufficiently correspond to the profiles of the primarily produced vacancy concentration Nvac. The absorption coefficient K(Nvac) determined from the depth profiles of the two magnitudes shows a square root dependence for GaAs, whereas for GaP a linear dependence is found. The differences observed are discussed in the frame of different nucleation mechanisms.

Investigation of defects by RBS-channeling methods

Abstract: The conventional RBS-channeling method permits the determination of the amount of displaced atoms in crystalline solids as a function of depth. The dependence of energy spectra of backscattered particles on the energy of the analyzing ions and on the temperature of the crystal to be investigated can give additional information about the geometrical configuration of displaced atoms and about the kind of defects in favoured cases. The physical basis of a discontinuous model for the dechanneling of ions by displaced atoms is described where especially the dependence of the Rutherford backscattering yield on the temperature is taken into consideration. The model is proved on typical examples as e.g. point defects in ion implanted GaAs layers, dislocation loops in ion implanted Si and lattice distortions in InxGa1−xAs crystals.