Defect Centers in Boron-Implanted Silicon

Abstract

Deep-level defect centers in the upper half of the energy gap, created by 70-keV and subsequent 150-keV boron ions implanted into n-type (111)-oriented silicon crystals at room temperature, have been investigated using the dark capacitance transient technique. Two independent centers with thermal ionization energy for electrons of 241 ± 8 and 558 ± 6 meV are found. Thermal emission rates of electrons at these centers depend slightly on the applied field. For annealing temperature up to 450 °C, the post-implantation annealing rates vary from 10−4/cm to 10−3/cm for both levels (defect concentration ∼ 1012 to 1013/cm3). The defects are annealed out (<10−4/cm) above 600 °C. The thermal activation energy and the preexponential factor in the emission rate are essentially independent of annealing temperature and no new centers are detected after each annealing step. Low junction leakage (0.2 μA/cm2 at −10 V) is observed for all samples obtained prior to and after annealing