implantation of Bi into GaP. II. channeling studies

The channeling technique has been used to investigate the properties of Bi-implanted Gap. Measurements of the crystal disorder for 100 keV room temperature implants indicate a damage vs dose curve corresponding to ～13000 displacements/ion in the linear region and saturation at ～1.5 × 10¹³ Bi ions/cm². Annealing of the radiation damage has been observed and indicates two annealing steps at ～450°C for light damage and ～750°C for implants in the 1 × 10¹⁴/cm² range. Difficulties associated with the thermal decomposition of the implanted area have been overcome with the use of SiO _x coatings. The experimental details associated with the use of the SiO _x layer and with the use of a C¹² beam to obtain better depth and mass resolution in the backscattering spectrum are discussed. The lattice location measurements of the Bi impurity show ～50 per cent of the Bi atoms to be along the 〈110〉 string after a 900°C anneal for a 7.5 × 10¹³/cm² implant. In addition, the spectra show ～25 per cent of the Bi atoms have diffused to the surface. Correlations of these lattice location results with measurements of the photoluminescent intensity of the GaP (Bi) isoelectronic trap show an agreement in trend with anneal temperature but indicate a factor of ～10 more substitutional ions in the channeling measurement as compared to the photoluminescence results.