ECE 3610 Chapters 9-12

anisotype junction

a heterojunction in which the type of dopant changes at the metallurgical junciton

electron affinity rule

the rule stating that, in an ideal heterojunction, the discontinuity at the conduction band is the difference between the electron affinities in the two semiconductors

heterojunction

the junction formed by the contact between two different semiconductor materials

image force-induced lowering

the lowering of the peak potential barrier at the metal-semiconductor junction due to an electric field

isotype junction

a heterojunction in which the type of dopant is the same on both sides of the junction

ohmic contact

a low-resistance metal-semiconductor contact providing conduction in both directions between the metal and semiconductor

richardson constant

the parameter A* in the current-voltage relation of a schottky diode

schottky barrier height

the potential barrier (phi bn) from the metal to semiconductor in a metal-semiconductor junction

schottky effect

another term for image force-induced lowering

specific contact resistance

the inverse of the slope of the J vs V curve of a metal-semiconductor contact evaluated at V=0

thermionic emission

the process by which charge flows over a potential barrier as a result of carriers with sufficient thermal energy

tunneling barrier

a thin potential barrier in which the current is dominated by the tunneling of carriers through the barrier

two-dimensional electron gas (2-DEG)

the accumulation layer of electrons contained in a potential well at a heterojunction interface. The electrons are free to move in the “other” two spatials

accumulation layer charge

the induced charge directly under an oxide that is in excess of the thermal-equilibrium majority carrier concentration

channel conductance

the ratio of drain current to drain-to-source voltage in the limit as Vds goes to 0

channel conductance modulation

the process whereby the channel conductance varies with gate-to-source voltage

CMOS

complementary mos; the technology that uses both p- and n-channel devices in an electronic circuit fabricated in a single semiconductor chip

conduction parameter

the multiplying coefficient of the voltage terms to obtain the MOSFET drain current

cutoff frequency

the signal frequency at which the input ac gate current is equal to the output ac drain current

depletion mode MOSFET

the type of MOSFET in which a gate voltage must be applied to turn the device off

enhancement mode MOSFET

the type of MOSFET in which a gate voltage must be applied to turn the device on

equivalent fixed oxide charge

the effective fixed charge in the oxide Q’ (ss), directly adjacent to the oxide-semiconductor interface.

feild-effect

the phenomenon by which an electric field perpendicular to the surface of a semiconductor can modulate the conductance

flat-band voltage

the gate voltage that must be applied to create the flat-band condition in which there is no space charge region in the semiconductor under the oxide

interface states

the allowed electronic energy states within the bandgap energy at the oxide-semiconductor interface

inversion layer charge

the induced charge directly under the oxide, which is the opposite type compared with the semiconductor doping

inversion layer mobility

the mobility of carriers in the inversion layer

metal-semiconductor work function difference

the parameter (phi ms) a function of the difference between the metal work function and semiconductor electron affinity

oxide capacitance

the ratio of oxide permittivity to oxide thickness, which is the capacitance per unit area, C ox

process conduction parameter

the product of carrier mobility and oxide capacitance

saturation

the condition in which the inversion charge density is zero at the drain and the drain current is no longer a function of the drain-to-source voltage

strong inversion

the condition in which the inversion charge density is larger than the magnitude of the semiconductor doping

threshold inversion point

the condition in which the inversion charge density is equal in magnitude to the semiconductor doping concentration

threshold voltage

the gate voltage that must be applied to achieve the threshold inversion point

transconductance

the ratio of an incremental change in drain current to the corresponding incremental change in gate voltage

weak inversion

the condition in which the inversion charge density is less than the magnitude of the semiconductor doping concentration

alpha cutoff frequency

the frequency at which the magnitude of the common-base current is 1/(2)^1/2 of its low-frequency value; also equal to the cutoff frequency

bandgap narrowing

the reduction in the forbidden energy bandgap with high emitter doping concentration

base transit time

the time that it takes a minority carrier to cross the neutral base region

base transport factor

the factor in the common-base current gain that accounts for recombination in the neutral base width

base width modulation

the change in the neutral base width with C-E or C-B voltage

beta cutoff frequency

the frequency at which the magnitude of the common-emitter current gain is 1/(2)^1/2 of its low-frequency value

collector capacitance charging time

the time constant that describes the time required for the B-C and collector-substrate space charge widths to change with a change in emitter current

collector depletion region transit time

the time it takes a carrier to be swept across the B-C space charge region

common-base current gain

the ration of collector current to emitter current

common-emitter current gain

the ratio of collector current to base current

current crowding

the nonuniform current density across the emitter junction area created by a lateral voltage drop in the base region due to a finite base current and base resistance

cutoff

the bias condition in which zero- or reverse-biased voltages are applied to both transistor junctions, resulting in zero transistor currents

cutoff frequency

the frequency at which the magnitude of the common-emitter current gain is unity

early effect

another term for base width modulation

early voltage

the value of voltage (magnitude) at the intercept on the voltage axis obtained by extrapolating the Ic vs Vce curves to zero current

emitter-base junction capacitance charging time

the time constant describing the time for the B-E space charge width to change with a change in emitter current

emitter injection efficiency factor

the factor in the common-base current gain that takes into account the injection of carriers from the base into the emitter

forward active

the bias condition in which the B-E junction is forward biased and the B-C junction is reverse biased

inverse active

the bias condition in which the B-E junction is reverse biased and the B-C junction is forward biased

output conductance

the ration of a differential change in collector current to the corresponding differential change in C-E voltage