22 Questions
What type of atoms are introduced into a semiconductor material to create a p-type material?
Trivalent
What is the characteristic of an n-type material?
It has excess electrons
What happens to the covalent bond when a pentavalent material is added to a semiconductor?
It is broken and an additional electron is introduced
Why are electrons in an n-type material relatively free to move?
Because they are loosely bound to the parent atom
What is the result of introducing impurities into a semiconductor material?
It remains electrically neutral
What type of atoms are used as donor atoms in n-type materials?
Pentavalent
What type of carriers are majority in an n-type material?
Electrons
What is the term for the vacancy of electrons in a covalent bond?
Hole
What type of impurities are used to create p-type semiconductor materials?
Trivalent
What is the result when an electron acquires sufficient energy to break from its covalent bond?
Creation of a hole
What is the effect of transfer of electrons and holes in an n-type material?
Increase in current flow
What happens to the parent atom when the fifth electron of a donor atom leaves?
It becomes positively charged
What is the term for the flow of electrons in a material?
Drift current
What is the type of semiconductor material resulting from the addition of pentavalent impurities?
n-type
What is the concentration of holes in a p-type silicon material with NA = 1x10^16 atoms/cm^3?
22,500 holes/cm^3
What is the electron mobility at 300 degrees K?
1300 cm^2 /V-sec
What is the concentration of electrons in an intrinsic silicon material at 3000 K?
1.5 x 10^10 electrons/cm^3
What is the effect of adding donor impurity atoms to an intrinsic semiconductor?
The concentration of free electrons increases
What is the concentration of electrons in an n-type silicon material with ND = 1x10^15 atoms/cm^3?
1x10^15 electrons/cm^3
What is the relationship between the concentration of free electrons and holes in an extrinsic semiconductor?
The concentration of free electrons is determined by the doping process
What is the conductivity of an n-type silicon material with ND = 1x10^15 atoms/cm^3?
0.208 (Ωcm)-1
What is the effect of adding acceptor impurity atoms to an intrinsic semiconductor?
The concentration of holes increases
Study Notes
Semiconductor Materials
- A p-type material is created by adding trivalent impurity elements to a semiconductor material with four valence electrons.
- Trivalent materials have acceptor atoms, which create holes (missing electrons) in the material.
N-Type Extrinsic Semiconductor Materials
- Impurities used for n-type materials have five valence electrons (pentavalent) and are called donor atoms.
- The most commonly used impurities are antimony, arsenic, and phosphorous.
- Donor atoms introduce free electrons in the material, which are loosely bound to the parent atom and are relatively free to move.
- The majority carriers in an n-type material are electrons.
- Minority carriers in an n-type material are holes, which are created when electrons acquire sufficient energy to break from their covalent bond.
Extrinsic N-Type Silicon Crystal Structure
- The addition of a pentavalent material creates an additional fifth electron, which is unassociated with the covalent bond.
- The fifth electron is relatively free to move within the material and requires less energy to enter the conduction band.
P-Type Extrinsic Semiconductor Material
- Impurities used for p-type materials have three valence electrons (trivalent).
- The most frequently used impurities are Boron, Gallium, and Indium.
- Acceptor atoms create holes (absence of electrons) in the material.
Carrier Concentration
- For p-type material, the concentration of holes (majority carrier) is pp ≈ NA = 1x10^16 holes/cm^3.
- The concentration of electrons (minority carrier) is np ≈ 22,500 electrons/cm^3.
- For n-type material, the concentration of electrons (majority carrier) is nn ≈ ND = 1x10^15 electrons/cm^3.
- The concentration of holes (minority carrier) is pn ≈ 225,000 holes/cm^3.
Law of Electrical Neutrality
- The doping process determines the concentration of free electrons and holes in an extrinsic semiconductor.
- The addition of donor and/or acceptor atoms creates ions due to the gain or loss of electrons.
- Acceptor atoms become negatively charged, and donor atoms become positively charged.
Learn about the creation of p-type materials by introducing trivalent impurities to semiconductor materials, and understand the difference between p-type and n-type materials in terms of covalent bonds and electron carriers.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
