Learn: Semiconductors Study Set

What are the three main types of solids?

Crystalline, polycrystalline, and amorphous.

Which type of solid has the most ordered atomic structure?

Crystalline.

What is a polycrystalline solid made of?

Many small crystals called grains with different orientations.

What are the interfaces between grains called?

Grain boundaries.

Which type of solid has no particular long-range atomic order?

Amorphous.

What example of an amorphous solid is given in the lecture?

Most glass.

What property measures how easily electrons move through a material?

Electrical conductivity.

What property measures how easily heat moves from hot to cold?

Thermal conductivity.

What property measures how much energy is needed to change temperature?

Heat capacity.

Which class of material is commonly used in wires and contacts?

Metals.

Which class of material is commonly used in transistors and diodes?

Semiconductors.

Which class of material is commonly used in dielectrics and substrates?

Insulators.

What is bandgap energy?

The energy needed to promote a valence electron to the conduction band.

Why do metals conduct easily according to the lecture?

They have plentiful free electrons in the conduction band.

Why do insulators conduct poorly?

The energy required to create free conduction electrons is very high.

What does the lecture say creates the bandgap?

The crystal structure.

What is silicon mainly used for according to the lecture?

Modern electronic devices and photovoltaics.

What bandgap value does the lecture give for silicon?

About 1.1 eV.

Which semiconductor has much higher electrical conductivity than silicon according to the lecture?

Germanium.

What bandgap value does the lecture give for germanium?

About 0.7 eV.

Which semiconductor alloy is used for high-speed and low-power devices?

Silicon-germanium, or SiGe.

What useful property of SiGe can be changed by changing composition?

Its bandgap.

Which semiconductor is highlighted for high-power and high-temperature devices?

Silicon carbide, or SiC.

What two major properties of SiC are emphasized in the lecture?

Very high thermal conductivity and stability.

Which semiconductor is highlighted for space and very-high-speed devices?

Gallium arsenide, or GaAs.

Why is GaAs useful in space applications?

It is resistant to radiation damage.

What bandgap value does the lecture give for GaAs?

About 1.42 eV.

Which wide-bandgap semiconductor is commonly used in blue LEDs?

Gallium nitride, or GaN.

What two properties of GaN are emphasized besides its wide bandgap?

Very high breakdown voltage and thermal stability.

What bandgap value does the lecture give for GaN?

About 3.4 eV.

Which semiconductor is commonly used for broadband lasers and optoelectronics?

Indium phosphide, or InP.

What bandgap value does the lecture give for InP?

About 1.34 eV.

Name one low-dimensional carbon material shown in the lecture.

Graphene, a carbon nanotube, or a buckyball.

What type of memory application are phase-change chalcogenides ideal for?

Built-in nonvolatile memory.

What two structural states are important in phase-change materials?

Amorphous and crystalline.

What superconducting particle pairing is named in the lecture?

Cooper pairs.

What magnetic phenomenon is associated with superconductivity?

The Meissner effect.

Name one application of superconductivity from the lecture.

Qubits, ultra-high-power electronics, or high-field MRI.

What material was the first transistor made from?

Germanium.

In what year was the first transistor made?

1947.

What is one major advantage of photolithography?

It is cheap and efficient because the whole wafer can be patterned at once.

What is the main limitation of photolithography given in the lecture?

Feature size is limited to greater than about 500 nm.

What is the main advantage of e-beam lithography?

It can produce features around 10 nm.

What is the main disadvantage of e-beam lithography?

It writes patterns one at a time, so it is slow.

Which deposition method is typically used for thin metal films?

E-beam deposition.

What environment is required for e-beam deposition?

High vacuum.

Which deposition method is typically used to grow semiconducting films?

Chemical vapor deposition, or CVD.

What does wet etching use?

Liquid acids or solvents.

Is wet etching generally directional or non-directional?

Non-directional; it etches in all directions.

What happens to wet-etch rate when temperature increases?

The etch rate increases.

What does dry etching or RIE use to create reactive species?

Plasma.

What provides directionality in reactive ion etching?

A strong electric field.

Which is generally faster according to the lecture: wet etching or dry etching?

Wet etching.

Which microscopy method is used for quick top-down inspection after lithography?

Optical microscopy.

Which microscopy method uses an electron beam for ultra-high-resolution images?

Electron microscopy.

Which microscopy method is best for surface roughness and cleanliness?

Atomic force microscopy, or AFM.

How does AFM measure a surface?

It drags an ultra-sharp tip across the surface and measures atomic forces.

As blackbody temperature increases, what happens to emitted intensity?

It increases.

As blackbody temperature increases, what happens to the peak wavelength?

It decreases.

What does the lecture define temperature as?

Mean kinetic energy.

What are the units of heat/thermal energy?

Joules.

Which has higher heat capacity in the lecture example: metal or water?

Water.

For the same energy input, which reaches a higher temperature: metal or water?

Metal.

What equation is shown for specific heat capacity?

Cp = Q / (mΔT).

What does Q represent in the heat-capacity equation?

Thermal energy.

What does m represent in the heat-capacity equation?

Mass.

What is Gibbs free energy used to describe?

The available energy and thermodynamic stability of a material system.

Which Gibbs free-energy state is the most stable?

The lowest Gibbs free-energy state.

What can prevent a system from quickly reaching its lowest free-energy state?

Activation energy.

What equation relates Gibbs free energy, internal energy, temperature, and entropy in the lecture?

G = H - TS.

At low temperature, which term matters more in the lecture's Gibbs discussion?

The internal-energy term H.

At high temperature, which term becomes more important?

The entropy term TS.

What does entropy measure according to the lecture?

Disorder or the number of available states.

What is the low-temperature water example in the lecture?

Water turning into ice.

What is the high-temperature water example in the lecture?

Ice turning into water.

What quantum particle is associated with light?

Photon.

What quantum particle is associated with electricity?

Electron.

What quantum is associated with heat and sound?

Phonon.

What quantum is associated with magnetism in superconducting matter?

Fluxon.

What equation is shown for photon energy?

E = hc / λ.

What equation is shown for photon momentum?

p = h / λ.

What is the lowest allowed electron energy state called?

The ground state.

What is a higher allowed electron energy state called?

An excited state.

What happens when an electron absorbs energy?

It can move to a higher energy state.

What happens when an electron drops to a lower energy state?

It releases energy.