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n materials (negative) have more electrons than holes. p materials (positive) have more holes (positive charge) than electrons.
You can have a look at Malvino book: Electronic Principles.
Semiconductors are materiels which can conduct electricity only if we gives energy (By increasing temperature) or by doping.
In normal cases without doping semiconductors like Si or Ge are electrically neutral,at T=0 K each silicon or germanium atom is linked to four others by covalent bonds. By increasing temperature covalent bonds get broken and electrons get free and can conduct electricity as well as the formed holes.
We can increase the conductivity of a semiconductor crystal not only be temperature but also by doping:
*If we put a trivalent atom (Boron) we get 3 bonds and a free bond which we call a hole so we have a positive carrier concentration more than negative so we get a p type semiconductor.
**If we put a pentavalent atom (Phosphore) we get 5 bonds and a free electron so we have a negative carrier concentration more than positive so we get an n type semiconductor.
For more infos we can see Microelectronic circuits by Sedra and Smith.
Regards,
One thing to keep in mind: Both P and N type materials are electrically neutral. N type materials have extra electrons that do not fit into the regualr crylstal pattern of pure silicon. P type materials have an absence of electrons to complete the regular crystaline structure of pure silicon. However, for either type the number of electrons equals the number of protons, and hence are elecrically neutral.
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