Question

How can we say germanium and silicon called semiconductors?

Answer 1

Hey mate

here you go!!!

Silicon. In solid state electronics, either pure silicon or germanium may be used as the intrinsic semiconductor which forms the starting point for fabrication. Each has four valence electrons, but germanium will at a given temperature have more free electrons and a higher conductivity.

It is well known that electrical power is stored, carried and propagated within the em fields. For the purposes of the transmission of power by such fields over long distances conducting materials such as Copper and Aluminium are used as they have the properties of having very small internal electric fields and allow the propagation of large electromagnetic fields where the bulk of the stored em energy resides. In such instances the electrical energy is propagated long distances within the em fields at close to the speed of light and not by the internal charges of the materials which move in the order of a few millimeters per hour.

Semiconductors, like microprocessor etc are made of materials which unlike conductors are readily able to control the internal electric field of such materials to allow the flow of electrical power power within and through them to be controlled, over very small distances, via charge carriers and not so much within the em fields. Very similar to the displacement current of capacitor. Thus when such materials have a very high internal electric field they are able to block the flow of internal charges and hence the propagating em fields in the connecting conductors and thus behave as an “insulator or high resistance” and when one is able to reduce the internal electric field then it allows the flow of internal charges to effectively connect (via the displacement current) and allow the propagation of externally applied em energy in the em fields. In this way semi-conductors are able to exhibit the properties of a controlled switch which may be controlled either continuously or discretely or hard switched and hence the term “semi-conductor”.

So although charges still move very slowly within any semiconducting material when considered over a few micro or nano-meters, millimeter per hour can become a million times faster at nano scale distances, and further improved through doping, which is why we are able to realise processors with speeds of several Gigahertz.

It simply relies on the ability of the material to establish and de-establish the internal electric fields and which allows them to have behave as a semi-conductor. Very smart science I would say and which goes to show that small things do count :)

Left to themselves in their pure, uncorrupted form, they are good insulators like diamond and carbon. Only insulators can be semiconductors. Even diamond / carbon can show the properties of semiconductors if similarly treated.They oppose / block electric flow. But add very very very little amount of impurity to them, their behavior changes drastically. They start conducting electricity.

Consequently, they can be doped ( programmed) to have certain conductivity by having a control over the percentage of the impurity atoms added. However, they can’t be classed as conductors that have free available conduction electrons naturally. In contrast, the semiconductors have a sort of forced conduction in them by corrupting them through the doping process and are not naturally available unlike the conductors