Scandium and Gallium Implantation Doping of Silicon Carbide
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S. YOSHIDA * and T. OHSHIMA ** *Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305-8568, Japan "*Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan ABSTRACT Rutherford backscattering, Raman spectroscopy as well as photoluminescence, resistivity and Hall measurements have been used to investigate the doping behaviour of Scandium and Gallium ions implanted into Silicon Carbide respectively. The recovery of the crystal lattice after implantation at room temperature followed by rapid thermal annealing is shown to be less effective in the case of Scandium compared with Gallium. Scandium implanted SiC exhibited a high resistivity in comparison to Gallium implanted crystals. INTRODUCTION Silicon carbide (SiC) is a promising wide bandgap semiconductor for high-power, hightemperature and high-speed electronic applications. The fabrication of semiconductor devices requires the modification of electronic properties of the material by doping. Thermal diffusion based techniques are precluded for this purpose because of the low diffusion coefficients of impurities in SiC at temperatures where the surface integrity can be maintained[ I]. Additionally, planar selective area doping is not possible that is crucial for making SiC integrated circuits. Therefore, ion implantation seems to be the only viable selective area doping method available for this material[2]. However, the electrical activation of p-type dopants has been found to be much lower in contrast to n-type dopants. In the case of p-type dopants most of the investigations were performed on Boron as well as Aluminium (Al) doped SiC[2-4] whereas less is known about the structural and electronic properties of Gallium[5-8] (Ga) and Scandium[911] (Sc) doped SiC, respectively. Therefore, SiC implanted with Ga or Sc is investigated in this article. The samples were characterized by Rutherford backscattering spectrometry / channeling (RBS/C), Raman spectroscopy, photoluminescence (PL), resistivity and Hall measurements. EXPERIMENT Epitaxial layers ([0001] orientation, n-type, off-axis, Si face, thickness: 5 pmn, carrier concentration: 8x1015 cm-3) grown on 6H-SiC substrates from Cree Research[12] were used as starting material. In order to obtain a uniform dopant concentration profile, a multiple-energy implant schedule was used (see Table 1). During implantation the substrates maintained at room temperature (RT) were tilted 7' with respect to the ion beam to minimize channeling effects. Ion range and nuclear energy distributions of the implanted dopants were calculated using the TRIM code (SRIM-97, full cascade)[131. A mean displacement energy of 25 eV for both C and Si atoms was used. The individual ion energies and fluences were determined using the results of this simulation. The total nuclear energy density distribution and the total dopant concentration are shown for Ga in Fig. 1 and for Sc in Fig.2, respectively. The critical energy density for the amorphization of SiC crystal at RT being 2x10 24 eV/cm 3 [14] is indicated
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