Why are doped semiconductors neutral

If it wasn't we would immediately feel it. In fact, it is a fun exercise to calculate how many electrons would be needed to generate a substantial force equivalent to, say, the weight of a car. The answer is surprisingly not very many.

This is because the electrostatic force is relatively strong. I am mentioning this to show that the substance would probably be not stable if it had even a small imbalance in the number of positive and negative carriers. Now, when people talk about P or N doping they mean the following. Each atom of P or N type material is also neutral. However, when placed near each other they cause interesting things to happen. Namely, one of the outer electrons of the N atom "feels" that P atom has a "hole" available more precise terminology would be a "quantum state".

Due to quantum mechanical effects, there is a non-zero possibility that the electron will transition to that hole. Once it transitions, the N now has one fewer electron and P has one extra electron. Now we have a bit of imbalance: N - slightly positive and P - slightly negative. This is precisely how the PN junction is formed. Forward bias means that we encourage the electrons to travel from N region towards P region. Of course, on the way between the two, they have to overcome the "natural" barrier that formed as described above.

This barrier is the typical 0. Sign up to join this community. The best answers are voted up and rise to the top. Create a free Team What is Teams? Learn more. How is a semiconductor electrically neutral? Ask Question. Asked 6 years, 5 months ago. Active 4 years, 4 months ago. Viewed 31k times. It has the same number of negative electrons as positive static atomic nuclei. What makes it "n-type" is that some electrons are not bound to static nuclei and thus can move freely and thus, act as charge carriers and conduct current.

The same logic applies to p-type as well. Add a comment. Active Oldest Votes. David Schwartz David Schwartz 3 3 silver badges 8 8 bronze badges. Community Bot 1. Korozjin Korozjin 3 3 silver badges 10 10 bronze badges.

The Photon The Photon k 3 3 gold badges silver badges bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. A semiconductor doped with a donor.

A free electron is now present. Donor impurities donate negatively charged electrons to the lattice, so a semiconductor that has been doped with a donor is called an n-type semiconductor; "n" stands for negative. Free electrons outnumber holes in an n-type material, so the electrons are the majority carriers and holes are the minority carriers. References "Chapter 6: Diodes.

That means, n-type and p-type materials are actually electrically neutral. The impurity added in p-type semiconductor provides extra holes known as Acceptor atom, whereas in n-type semiconductor impurity provides extra electrons and termed as Donor atom. In a p-type semiconductor, the majority carriers are holes, and the minority carriers are electrons. The effective mass of charge carriers usually effect the mobility and hence the conductivity of semiconductors.

The effective mass of electrons is usually lower than that of holes and therefore, the conductivity is generally high for n-type semiconductors.