Defects and Oxygen in Silicon Studied by Positrons

During the last few years wide interest is generated in applying the positron annihilation techniques to defects in semiconductors. Since defects in semiconductors are, in many regards, dissimilar to defects in metals one must expect that new responses from positrons will emerge not normally associated with metals. One such important effect would be the charged state of a defect in a semiconductor. At the present time silicon is the semiconductor which has been investigated mostly, but the important III–V GaAs compound semiconductor is currently also under intensive investigations. For the case of silicon a detailed review will be presented encompassing lifetime results for vacancy agglomerates, high-temperature equilibrium measurements (undoped and P-doped) and oxygen in silicon. Furthermore, indications for the temperature variation of the bulk lifetime and its possible variation with doping levels will also be discussed.