Once we know the density of electrons and holes, we need to see how they respond to an electric field and how much current they generate. Here we focus on electrons but the same concepts apply to holes and to avoid very busy visualizations we only consider a few electrons.
Follow the electrons and see if there is a net flow of carriers
if you wait for a while.
You can select to see the traces of
electrons in the x and y directions.
The random movement of
electrons is due to their thermal energy and is called
thermal velocity.
Show X-axis speed vectors
Show Y-axis speed vectors
Click on the box to the right to apply an electric field. You can
change the direction and intensity of the electric field by
clicking away from the center of the box.
· What happens to the velocities of electrons in the x and y
directions?
· Is there a net flow of electrons?
· What do you think determines how much electric current
you will have?
· The average velocity of electrons in the opposite direction of
the electric field is called “Drift Velocity.”
· How does this drift velocity change with electric field?
· How does this drift velocity compare with the average thermal
velocity of electrons?
Show X-axis speed vectors
Show Y-axis speed vectors
Click on the box to the right to apply an electric field.
· What happens if you increase the electric field too much?
Can you guess why the drift velocity saturate?
· You may want to check the average time between scatterings
(toggle below).
Drift Velocity or Scattering Time
Show X-axis speed vectors
Show Y-axis speed vectors
Click on the box to the right to apply an electric field.
Adjust Temperature here
Show X-axis speed vectors
Show Y-axis speed vectors