Extra Practice Questions Flashcards
(39 cards)
Which Classes of materials have band gaps?
Insulators & Semi-Conductors
What is Fermi lvl (EF) and how does it relate to the Fermi Function?
The Fermi lvl is the value of energy when the Fermi Function f(EF) =0.5
What is a legitimate reason to use Silicon technology for electronics (Assume microelectronic devices), and Why?
Silicon (Si) can easily be doped because it’s Easy to infuse Si with something that has more/less valence electrons to change it’s conductivity.
True or False: A Wide Band Gap makes is easier for electrons to conduct
False: Wider band gap doesn’t make it easier to conduct e-
How many electrons are in Valence Bands in Semi-Conductors & Insulators?
in Semi-Conductors & Insulators, the Valence Bands are Full.
Which of the following is true of metals?
a) All the possible electron states are connected; there is no break in energies between states.
b) All the possible electron states are always occupied; there are no available unoccupied states.
c) There are empty states directly above occupied states without a break in energies.
d) There are empty states directly below occupied states without a break in energies.
a) Proven false by metal band diagram’s first case - Has a break
b) If every state was already occupied, metals couldn’t conduct
c) In case 1 of the metal band diagram’s the empty state is right above occupied states
d) Look at c)
Describe the 2 cases that can produce metals/conductor properties (Metal Band Diagrams)
Case 1) The occupied state is at the very bottom, and is filled with electrons. The Empty state is right above the occupied state, and there is a gap between the empty state and the Conduction Band
Case 2) There are 2 Bands that overlap. The above band 1 is empty, and the band 2 beneath it contains electrons. The overlap allows the e- states in Band 1 to move into Band 2 with any amount of energy, so it can conduct into these states.
How would you expect the drift velocity of electrons to change in a semiconductor when the applied voltage increases from –1V to 0V?
The magnitude of the Drift Velocity will Decrease, b/c using the formula of the Electric Field E =V/d we can compare initial & final magnitudes and see whether it increase or decreases. Magnitude of I -1 I is larger than I 0 I so the magnitude decreases thus Drift Velocity decreases magnitude aswell.
Insulators do not allow current to flow easily, but neither does vacuum, so why do we bother to insert dielectrics between the parallel plates of our capacitors?
Presence of the Dielectric Increases amount of charges we can store on the plates.
Capacitors can hold Both…
Capacitors can hold Both: Charge (In the plates) and Energy (In the dielectric)
Which of the following is an incorrect statement about capacitors?
a) Switching to plates with higher dielectric constants increases capacitance.
b) Switching to dielectrics with lower dielectric constants increases capacitance.
c) Using a metal in place of a dielectric increases surface charge density.
d) Applying a stronger external voltage to a capacitor will increase its capacitance.
e) All Of The Above
a) Dielectric constant of dielectric matters only not the plates
b) C is proportional ∝ to ε (epsilon)
c) If put metal btwn plates, there nothing holding charges apart, since charges can flow through conductive metal
d) False
e) All Of The Above
What does the Dielectric Constant Represent?
How well we are able to Polarize a material.
Why might you expect the dielectric constants of polymeric materials with lots of cross-linkages to decrease at lower applied signal frequencies than those of polymeric materials with very few cross-linkages?
Changes in Orientation-based polarization since it is at the lowest frequency and is the first to fall off (Remember the εr vs f(Hz) graph). It is more difficult to polarize at a Higher Frequency for turning large objects.
What are Electronic Energy bands?
Allowable energy states for electrons
What is a Work Function
Energy needed to pull an electron off a metal
What is the Matthiessen’s rule, and what type of material does it apply to?
Matthiessen’s rule: Ptotal = Po + ∝ ΔT + Pi + Pd only applies to metals. (Row total = Thermal conductive component of resistivity of an ideal metal + contribution of resistivity from impurities + contribution from deformation of martials)
Parallel plate capacitors usually have _____ between their plates
Parallel plate capacitors usually have Insulators/Dielectrics between their plates
What are Capacitors commonly used for? (Applications)
Surge Protection, AC-DC conversion, Energy storage, and Sensing
Is this the symbol for the Permeability of a vacuum: εo
No: εo is the symbol for Permittivity, μ0 is the symbol for Permeability of a vacuum.
Is an acceptor a substitution atom that contributes at least two surplus electrons?
No, Acceptor: Happens If we dope a S.C with something that has fewer valence e- and creates holes.
Which of the following is ALWAYS true of the band structure for a conductor?
a) The conduction band and valence band never overlap
b) The conduction band is empty
c) There are open states available to electrons that are already at 𝐸𝑓
a) Represents a different type of conductor
b) Represents a different type of conductor
c) Will always have open states available for electrons that are already at Ef (directly adjacent)
What happens if you apply a forward-bias to a PN junction?
Flows from Anode to the Cathode
True or False: weaker doped regions account for more of the width of the depletion region?
True: Because weaker doped regions has fewer charge carriers, so the depletion region has to go further into that region to recover same amount of charges.
The role served by Resist in the production of semiconductor devices is to:
Create a Mask - From the oxide layer on top of Si then create different doped regions
