Question

Given the semiconductor indium antimonide (InSb):

Suggest possible impurities that would make InSb n-type, p-type, isoelectronic, or amphoteric.

Answer 1

Indium antimonide(InSb) is the narrow band gap (band gap ~0.17eV at room temperature) semiconducor made up of Indium (In) and antimonide(Sb). It comes in the III-V group of semiconductor like GaAs ,GaN, etc.

a) n-type semiconductor are formed when we have excess of electron which forms a donor level in the band gap. Thus in III-V group InSb, doping impurities from group VI element like Te, Se such that it will replace Sb would make n-type InSb.

b) p-type semiconductor are formed when we have excess of holes(absence of electron) which forms an acceptor level in the band gap. Thus doping impurities from group II like Cd,Zn, etc such that it will replace In would make p-type InSb.

c) Isoelectronic semiconductors are formed when the another element from the same group replaces each other . In case of InSb, when In is replaced by another group III elements like Ga,Al,etc and Sb is replaced by another group V element like As,P,etc. then we get isoelectronic InSb.

d) Amphoteric semiconductors are formed when both donore and acceptor levels are formed in the band gap. Thus when group IV elements like Si,Ge are doped in InSb, it can replace In as well as Sb. When In is replaced, then donor level if formed and when Sb is replaced then acceptor level is formed.