Features of thermal and radiation defect formation in silicon doped with holmium

Full text: The problems of defect formation in silicon are one of the actual problems in study of semiconductor materials and microelectronics, because the process of the fabrication practically of any semiconductor devices comprises different cycles of thermal processing. To modify the characteristics of silicon (increasing the photosensitivity, tenzosensitivity, changing of resistivity etc.), its doping with different impurities, influence with ionizing radiations that finally brings to the formation of different sort of defects. In this work the results of complex investigations of thermal and radioactive defect formation in silicon doped with holmium are given. As investigated samples n-Si doped with holmium, and the control samples n-Si with identical electric parameters were used. From the measurements of samples n-Si with DLTS and PC methods, was shown that atoms of holmium do not create deep levels in forbidden zone of the base structures Au-Si-Sb, though their full concentration in silicon volume, accordingly to neutron-activation analysis constitutes 1016-1018. It was shown, that high temperature processing of Au-Si-Sb structure in interval of the temperatures from 900 deg C to 1250 deg C and different range of time from 0,5 to 50 hours brings to appearance of two deep levels with energies Ec-0,38 eV and Ev +0,29 eV. Efficiency of creating those levels depends on concentrations of holmium atoms, temperature of processing and presence of oxygen in initial silicon doped with holmium. Investigations with gamma irradiation of Au-Si-Sb structures do not render observable influence to the parameters connected with deep level (energy of ionizing and section of the seizure of current carriers). It was discovered, that presence of Ho in Si delays the efficiency of formation known radiative defects-complexes, vacancy-oxygen (A-centre) and vacancy-phosphorus (E-centre). (author)