Quick conceptual question about semiconductors

[Wheelwalker]

Homework Statement

"Based only on the desire to limit minority carriers, why would silicon be preferable to germanium as a fabric for doped semiconductors?"

Homework Equations

N/A

The Attempt at a Solution

Silicon has a band gap of approximately 1.1 eV while the band gap of germanium is around 0.7 eV. Thermal excitation is more prominent in low band gap materials, so silicon would be preferable due to its larger band gap. My question is, wouldn't thermal excitation also allow more majority carriers to enter the conduction band? Also, in the practical application of semiconductors, is it generally desirable to limit minority carriers? If so, why?

 

[mark726]

I would like to provide some clarification on the topic of minority carriers and their importance in semiconductors. Minority carriers refer to the type of charge carriers (electrons or holes) that are present in a semiconductor material in lower concentrations compared to the majority carriers. In the case of doped semiconductors, the majority carriers are the ones introduced through the doping process, while the minority carriers are the ones that are naturally present in the material.

Now, the question at hand is why silicon is preferred over germanium as a fabric for doped semiconductors in order to limit minority carriers. To understand this, we need to first understand the concept of doping in semiconductors. Doping refers to the intentional introduction of impurities into a semiconductor material in order to alter its electrical properties. These impurities, also known as dopants, can either donate or accept electrons, thus creating either an n-type or p-type semiconductor.

In the case of silicon, it is a tetravalent material, meaning it has four valence electrons. When doped with a pentavalent impurity such as phosphorus, it creates an n-type semiconductor. This means that the majority carriers in silicon are electrons, while the minority carriers are holes. On the other hand, germanium is a trivalent material, meaning it has three valence electrons. When doped with a pentavalent impurity, it creates a p-type semiconductor, where the majority carriers are holes and the minority carriers are electrons.

Now, coming back to the question of why silicon is preferred over germanium to limit minority carriers, the answer lies in the fact that in a doped semiconductor, the concentration of minority carriers is directly proportional to the concentration of majority carriers. This means that by limiting the concentration of minority carriers, we can also limit the concentration of majority carriers. In the case of silicon, since the majority carriers are electrons, by limiting the concentration of minority carriers (holes), we can also limit the concentration of electrons. This is because the holes act as traps for electrons, thus reducing their mobility and concentration.

In practical applications of semiconductors, it is generally desirable to limit minority carriers in order to improve the efficiency and performance of the device. This is because minority carriers can cause unwanted recombination processes, reducing the overall electrical conductivity of the material. By limiting the concentration of minority carriers, we can reduce these recombination processes and improve the overall performance