Fermi-level dependence of formation of hydrogen molecules in crystalline silicon

We report a systematic investigation on the Fermi-level dependence of the formation of two different types of hydrogen molecules in silicon. Hydrogen molecule at the tetrahedral (T) site (H-2(T)) is formed only in heavily doped n-type below 200degreesC, but is observed both in the n- and p-type above 200degreesC. The temperature dependence is due to the increase of the thermally activated carrier concentration. The possible precursors of the H-2(T) are H+(BC) and H-0(BC) in the p-type, and H-(T) and H-0 in the n-type. The Fermi level dependence of the formation of the hydrogen molecule trapped in platelets (H-2(p)) above 250degreesC is very different from that below 250degreesC. The result suggests that platelets are formed from hydrogen-complexes other than the H-2(*) above 250degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.