UNIT 1: SEMICONDUCTOR Practice Flashcards

Vocabulary flashcards covering semiconductor fundamentals, energy band theory, doping types, Fermi-Dirac statistics, and junction physics.

Binding Energy ($E_b$)

The energy released when $N$ atoms combine to form a solid, defined by the equation $NA_g \rightarrow NA_s + E_b$.

Pauli's Exclusion Principle (Solid Formation)

The principle responsible for the splitting and broadening of individual energy levels into bands as atomic wave functions start to overlap.

Valence Band

The last filled energy level at $T = 0\,K$.

Conduction Band

The first unfilled energy level at $T = 0\,K$. The energy level of this band is higher than that of the valence shell.

Semiconductor

A material with electrical properties between a conductor and an insulator, exhibiting a negative temperature coefficient of resistance where resistance decreases as temperature increases.

Doping

The process of adding impurities to semiconductors to increase their conductivity.

Free Electrons

Electrons that have gained enough external energy to break away from the nucleus and become disconnected from their respective atoms.

Forbidden Gap ($E_G$)

The energy gap that separates the conduction and valence bands where no electrons can normally exist.

Insulator (Energy Band Definition)

A material with an extremely wide forbidden gap (e.g., $E_G = 6\,eV$) which prevents valence electrons from jumping into the conduction band.

Intrinsic Semiconductor

Semiconductors in their purest possible form, typically containing impurities as low as 1 part in 100 million.

Extrinsic Semiconductor

Semiconductors obtained from intrinsic ones by adding impurities (dopants) to increase conductivity.

Donor Impurity

A pentavalent dopant atom containing five valence electrons (e.g., Antimony, Arsenic, or Phosphorus) used to manufacture n-type semiconductors.

Acceptor Impurity

A trivalent dopant atom containing three valence electrons (e.g., Boron, Gallium, or Indium) used to manufacture p-type semiconductors.

n-type Semiconductor

A semiconductor where majority charge carriers are electrons and the donor energy level is very close to the bottom of the conduction band.

p-type Semiconductor

A semiconductor where majority charge carriers are holes and the acceptor energy level is very close to the top of the valence band.

Direct Gap Semiconductor

A class of semiconductor where the conduction band minimum and valence band maximum occur at the same wavevector value ($k = 0$), allowing for light emission (e.g., GaAs).

Indirect Gap Semiconductor

A class of semiconductor (e.g., Silicon) where a transition from the conduction band minimum to the valence band maximum requires a change in wavevector ($k$), generally giving up energy as heat.

Fermi Level ($E_F$)

The energy level representing the top of the collection of electron states at absolute zero, or the level where the probability of finding an electron is exactly $50\%$.

Fermi-Dirac Distribution Function ($f(E)$)

The probability that an available energy state at $E$ will be occupied by an electron at absolute temperature $T$, defined as $f(E) = \frac{1}{1 + e^\frac{E - E_F}{kT}}$.

Law of Mass Action

The principle stating that the product of electron ($n$) and hole ($p$) concentrations is constant at a specific temperature, expressed as $np = n_i^2$.

Invariance of Fermi Level at Equilibrium

A principle stating that no discontinuity or gradient can arise in the equilibrium Fermi level $E_F$ across materials in contact.

Built-in Potential Barrier ($V_0$)

The potential barrier in a p-n junction that maintains equilibrium, preventing current from being produced by the junction voltage alone.

Forward Bias

A circuit configuration where the positive battery terminal connects to the p-side and the negative to the n-side, decreasing the depletion region and barrier height.

Reverse Bias

A circuit configuration where the positive battery terminal connects to the n-side and the negative to the p-side, increasing the depletion layer width and barrier height.

Drift Velocity ($v_d$)

The extra velocity acquired by charge carriers in the presence of an applied electric field, proportional to the field strength ($v_d = \mu E$).

Mobility ($\mu$)

The constant of proportionality defined as the drift velocity per unit electric field, measured in $m^2/V-sec$.