Question

Is copper a semiconductor?

Answer 1

Hint: Recall that a semiconducting material selectively conducts current depending on the configuration of its terminals with respect to the battery. Also recall that semiconductors do not have as many free electrons and their conductivity increases with an increase in temperature. Now, it is known that copper is a metallic element. In such a case, it is bound to have a large number of free electrons. To this end, deduce how its conductivity would be affected with rising temperatures and arrive at a suitable conclusion about its conductive nature.

Complete answer:
We know that solids can be broadly classified into metals, semiconductors or insulators based on their conductive properties. We know that copper conducts electricity. But so do semiconductors. So let is comprehensively deduce the distinction between metals(conductors) and semiconductors and understand to which category copper belongs to, keeping in mind that copper is metallic in nature.
Now, metals or conductors always allow current to flow through, whereas semiconductors conditionally allow current to flow through, depending upon their structural and circuital configuration. Conductors usually have a large number of free electrons and their conductivity is based on their motion whereas semiconductors have a low number of free electrons and their conductivity is thus based on the motion of electrons and holes. The resistivity of a conductor increases with increase in temperature whereas the resistivity of a semiconductor decreases with an increase in temperature.
The resistivity of a conductor increases with mixing impurities whereas the resistivity of a semiconductor decreases when mixed with impurities.
We empirically know that copper, being metallic in nature, has a large number of free electrons that are capable of carrying out unimpeded conduction irrespective of its orientation in a circuit. We also know that when copper is heated, the collision of electrons increases with the absorption of thermal energy, leading to a decrease in conductivity or an increase in its resistivity. Also, adding impurities to copper increases its resistivity since the impurities act as barriers to electron flow thereby impeding the current flowing through it. We can thus conclude that the properties of copper are extremely consistent with the defining properties of conductors due to which we can say that copper is not a semiconductor.

Note:
Though copper is not a semiconductor, it finds an application in semiconductor technology. Due to the unconditional conductive property of copper, it is often used as interconnects between elements of integrated circuits (ICs) since it minimizes propagation delays and reduces power consumption. But copper interconnects are usually coated with a barrier metal layer since copper acts like a semiconductor-killer. This is because diffusion of copper into semiconducting parts of an IC degrades their semiconducting properties and prevents the corresponding transistors from appropriately functioning, due to which a layer must exist to separate the copper from the silicon.