SEMICONDUCTORS Flashcards
NCERT ACTIVE RECALL (EXTRA POINTS, REST REFER VIVA QS AND HIGHLIGHTED ONES) (18 cards)
CRT FULL FORM? USED IN? WORK IN PRINCIPLE OF? BEING Replaced by? Monitors by?
CATHODE RAY TUBE, TELEVISION, COMPUTER MONITORS
VACCUME TUBES
LCD (Liquid crystal display)
Supporting solid state electronics
Before the implication of semiconductor devices something came up and how was it used to detect what?
Naturally occurring crystal of GALENA (LEAD SULPHIDE, PbS) With metal point contact attached to it.
Used as detector of radio waves
On the basis of relative values of electrical conductivity or resistivity solids are classified as?
Also discuss their possession of resistivity or conductivity
Metals , Low resistivity or high conductivity
Semiconductors, Intermediate resistivity of Conductivity if compared to metals and insulators
Insulators, High resistivity or low conductivity
What are the elemental semiconductors?
Silicon Si, Germanium Ge
Most of the currently available semiconductor devices are based on?
Silicon Si, Germanium Ge And compound inorganic semiconductors
What are energy bands?
Inside crystal-each-electron-unique position-no two electrons- see- same pattern- surrounding -charges
Due to this, each electron- have- diff energy level.
These diff energy levels-continuous energy variation form - called energy bands
DEFINE valence band
Define conduction band
energy band-includes-energy levels-of-valence electrons
Energy band above valence band- conduction band
When can electrons from the valence band easily move into conduction band ?
lowest level-conduction band-happens-lower-than-highest level-of-valence band
What is the case with metallic conductors?
Normally-conduction-band-empty
sometimes-overlaps-on-valence-band-electrons-move-freely
How does an insulator happen?
gap-b/w-conduction band and valence band- electrons-in - valence band- remain bound- no free electrons- available in conduction band
define energy gap
Gap-b/w-top-valence band-and-bottom-conduction band- called energy band gap
When do bonds stay intact with elements like Si and Ge?
no bonds - broken, arises at low temp
Define hole
effective positive electronic charge
Intrinsic semiconductors me what is equal to what?
number of free electrons nₑ = no of holes nₕ
What cannot be done with extrinsic semiconductors and how can it be achieved?
no imp electronic devices can be created
by using impurities
What are the two types of dopants? used in doping?
Si and Ge
pentavalent (valency 5)- AAP
Trivalent (valency 3) - BIA
How n type arises?
speciality of n type semiconductors
Doping with pentavalent element
electrons-majority-carriers
holes-minority-carriers
