Annealing effect for heavily Sn-implanted GaAs

Rutherford backscattering spectrometry, transmission electron micrography, and the Hall measurement have been used to investigate the lattice site location, residual defects, and activation behavior of Sn-implanted GaAs. Undoped GaAs (100) wafers were implanted with 150-keV Sn+ ions to doses of 5×1014–3×1015/cm2 at room temperature and annealed at 850 °C for 15 min with a Si film cap. Transmission electron micrographs for annealed samples showed that the residual defects were dislocations. The precipitation of Sn was observed in 1×1015 and 3×1015/cm2 implanted samples. The electrical activation efficiency has been measured to be 1.1%–2.6% by Hall measurement, and the peak carrier concentrations for all the annealed samples were 1×1018/cm3. The channeling Rutherford backscattering showed that 35%–88% of implanted Sn atoms were located in the substitutional lattice sites. It was found that only about 3% of substitutional Sn atoms in GaAs were activated as donors.