1. Silicon is doped with 5𝑥10¹⁷ phosphorous dopants per cm³.
Assume all of the dopants are ionized, and the electron mobility is 500 cm²/V.sec. The silicon is patterned into a 5nm nanowire, which is 100nm long, and we would like to build a junction
FET with a wrap-around gate.
How many dopant atoms will be in the conducting channel of that transistor?
What is the Fermi level of the conducting channel?

2. A N-MOSFET transistor is formed with a planar silicon geometry, with a source, drain and polysilicon gate.
The gate length is 0.13 microns, and a source-drain voltage of 2V is applied.
What is the electric field?
What is the saturation velocity?
What is the carrier transit time?
Repeat the calculations for 60nm, 45nm and 22nm gate lengths.
How does the carrier transit time relate to the maximum frequency of the transistor?

3. The MOSFET from question above is constructed by using a 5𝑥10¹⁸ doped n-layer implanted into a 10¹⁶ doped p-type substrate.
If the area of the source and drain contacts are 1x1 micron, what is the current in the transistor when the gate is turned off?
Describe the concept of inversion?
What will be the threshold voltage if a poly-silicon gate is used?
List assumptions you had to make.

4. If a 10mW red laser with wavelength of 650nm is used to irradiate a GaAs thin film that is 220nm thick, how much of that light is absorbed?
How many electron-hole pairs are generated?
If the optical quantum efficiency of the GaAs is 50%, how much power is emitted from the GaAs?
How much heat is dissipated in the film?

1. Silicon is doped with 5𝑥10¹⁷ phosphorous dopants per cm³. Assum...