Hi!

Semiconductors are substances which are not either conductors or non-conductors. For example, their electric conductivity is not as good as conductors and also not as bad as the non-conductors. They are between them. At absolute zero, they do not conduct electricity. Examples of Semiconductors are Silicon, Germanium. Gallium, Arsenide, Cadmium, Selenide are also Semiconductors.

I have already answered your query on difference between metals and alloys.

Hope this is helpful!

All the very best!