DIFFUSION OF SHALLOW IMPURITIES IN SILICON

The diffusion in Si of shallow impurities from columns III and V of the periodic table has been the subject of many experimental studies. However, the identification of the diffusion mechanisms responsible for these elements remains a hotly debated issue in the literature. We review the experimental evidence which shows some dopants to diffuse primarily by interstitial-assisted mechanisms while others are dominated by the vacancy mechanism and address the question of why one type of mechanism may dominate over the other for a particular dopant. We also show new data the behaviour of Ga and Ge diffusion in the presence of excess silicon interstitials or vacancies. The possible importance of Ge diffusion studies to questions concerning Si self-diffusion is discussed.