Positron annihilation in boron-implanted n-type silicon

The ion damaged effect and subsequent isothermal annealing in boron-implanted Si was studied by positron annihilation lifetime measurements. The mean positron lifetime in preimplanted n-type Si is 243 psec. The variation of mean lifetime is detectable when the implanted boron dose is greater than 1.0x10¹⁵/cm². The saturated mean positron lifetime (247 psec) occurs when the implantation dose reaches 2.5x10¹⁵/cm². The mean electron density of the positron sensitive defects is estimated to be about 85% less than that in the perfect parts of the crystal. Isothermal annealing was held in every 5-minute step at 1000°C. In the first step, the positron lifetime in the implanted sample increases slightly and then decreases completely to its initial state in the 3rd step. Sheet resistance of the sample monitored by 4-point probe method has been found closely related to the positron lifetime.