2 、 in order to solve the phenomenon of the outdiffusion of the base dopant , two solutions are suggested : 1 ) the sige : c base can effectively solve the outdiffusion problem ; 2 ) the undoped buffer layer can constrict the outdiffusion phenomenon 2 、為了解決基區(qū)雜質(zhì)外擴(kuò)現(xiàn)象,提出了兩種方案: 1 )采用摻碳的sige : c基區(qū)層,能夠有效消除外擴(kuò)問(wèn)題; 2 )采用未摻雜的緩沖層i - sige ,能夠有效抑制外擴(kuò)現(xiàn)象。