Question 25.4: State whether each of the following combinations of elements...
State whether each of the following combinations of elements could form a semiconductor:
(a) Ga-Se, (b) In-P, (c) Cd-Te
Strategy Count the valence electrons in each type of atom. If they total eight for the two elements, then the combination will probably form a semiconductor.
Setup Locate each element in the periodic table. All of them are main group elements, so we can use their group numbers to directly determine the number of valence electrons each element contributes: (a) Ga is in Group 3A, and Se is in Group 6A. (b) In is in Group 3A, and P is in Group 5A. (c) Cd is in Group 2B, and Te is in Group 6A.
(a) Ga has three valence electrons, and Se has six. This gives a total of nine, which is too many to form a semiconductor.
(b) In (three valence electrons) and P (five valence electrons) combine for a total of eight, so In-P should be a semiconductor.
(c) Cd (two valence electrons) and Te (six valence electrons) also combine for a total of eight, so Cd-Te should be a semiconductor, too.