Semiconducting highly thallium doped silicon prodn. - by doping melt with thallium alloy to reduce thallium vapour pressure and drawing

摘要

Prodn. of semiconducting, highly T1-doped Si (I) entails first producing a metallic alloy (II) contg. T1, then fusing this with Si in a crucible and drawing a highly doped Si rod or bar from this. Pref. (II) is an alloy of T1 (1 wt.pt.) with Au (4 pts.), Ag (4 pts.) or Sn (3 pts.). T1 is incorporated in a concn. of ca. 10 exp. 18 or 10 exp. 19 T1 atoms/cm3. Ar under slight over-pressure is used as protective gas. (I) is specified for making opto-electronic devices and IR sensors. The use of (II) as dopant greatly reduces the T1 vapour pressure and hence considerably increases the possible T1 concn.