Week 1A: Introduction to Semiconductor Physics

Silicon

Most used electronic material; Atomic number = 14.

Conduction Band

Electrons here are mobile and are no longer associated with any particular atom.

0K

Conduction Band is empty at ____ (temperature).

Valence Band

Electrons here are tightly bound to their atoms and constrained from moving.

4 electrons

How many electrons does Silicon have per atom at 0K in the Valence Band?

Forbidden Band

Contains no available energy states for electrons.

Insulator

Gap between valence band and conduction band is greater than 9eV.

Insulator

Has an empty conduction band and full valence band.

Semiconductor

The forbidden gap is ~1eV long.

Conductor

There is an overlap between the conduction band and the valence band.

Conduction Band

A material cannot support current flow if the ____ is empty.

Crystalline, Amporphous, Polycrystalline

Types of Solids

Crystalline

Atoms are regularly arranged in three dimensions.

Amorphous

Atoms irregularly arranged.

Polycrystalline

Crystalline clumps are irregularly arranged to form a solid.

Elemental and Compound

Two basic types of semiconductor materials.

8 electrons

How many electrons should be shared between two elements in a compound semiconductor?

Boron, Aluminum, Gallium, Indium, Thallium, Nihorium

Elements found under IIIA in the periodic table.

Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Moscovium

Elements found under VA in the periodic table.

Carbon, Silicon, Germanium, Tin, Lead, Flerovium

Elements found under IVA in the periodic table.

Covalent Bond

What type of bond is formed between Silicon and other elements?

Tetrahedral crystalline structure

What type of structure does a Silicon have?

sink, float

Electrons tend to ____ while holes tend to ____.

Intrinsic Semiconductor

Semiconductor in its purest form.

Insulator

At 0K, semiconductor behaves like a/an ____.

True

T or F: Both electrons and holes contribute to current flow.

opposite, same

Electrons tend to move (opposite, same) the direction of an electric field while holes tend to “move” in the (opposite, same) direction as an electric field.

Intrinsic Carrier Concentration

The number of conducting electrons in an intrinsic semiconductor per unit volume in thermal equilibrium.

1.5 × 10^10/cm³ at 300K

ICC of Silicon (Indicate the temperature. Hint: room temp).

Extrinsic Semiconductor

Semiconductor with impurities added to enhance its electrical properties. Also called “doped” semiconductors. Impurities are called “dopants.”

Donor Impurities and Acceptor Impurities

Two types of impurities.

Degenerately doped

Term for an excessively doped semiconductor.

Donor Impurity

They can donate a free electron. Impurity contains 5 valence electrons (Group V of the periodic table).

negative, n-type

Donor Impurity = more (positive, negative) charge carriers. Classified as (n-type, p-type).

Acceptor Impurity

Impurity contains 3 valence electrons. Group III of the periodic table.

positive, p-type

Acceptor Impurity = more (positive, negative) charge carriers. Classified as (n-type, p-type).

Total ionization

All the dopant atoms have donated (or accepted) their carriers.

Total negative charge = n + Na

Total positive charge = p + Nd

Assuming total ionization, what is the formula for the total negative charge and the total positive charge?

Crystalline semiconductors

Most electronic devices, especially those found in integrated circuits, use this type of semiconductor.

True

T or F: The Mass Action Law does not apply to degenerately doped semiconductors.

False

T or F: The Mass Action Law is applicable even if there is no thermal equilibrium.