4.1 Semiconductors - Diodes Flashcards
What are semiconductors?
element or compound that contain relatively few free moving electrons / have a small band gap between valence band and conduction band
Which elements are the most important semiconductors? (4)
- Silicon
- Germanium
- Selenium
- Copper oxide
What is doping?
the shifting of balance of electrons by adding (doping) other atoms to silicon.
what is an n-type semi conductor?
atoms with one more valence electron than the pure semiconductor are added to it (n-type = negative because the global charge is negative)
what is an p-type semiconductor?
atoms with one less valence electrons than the pure semiconductor are added to it (p-type = positive charge)
what is the temperature limit of an impure material?
+75c germanium
+150c silicon
What is the diffusion voltage of germanium and silicon?
germanium = 0.3V
silicon = 0.7V
what can a semiconductor do?
block or let current through
if the positive pole of a current is in the n-zone and negative pole in the p-zone, what happens?
a depletion zone forms at the junction (no free electrons or empty spaces) and the semiconductors blocks the charge / Reverse Biased
if the negative pole is in the n-zone and positive pole in the p-zone, what happens?
the depletion layer breaks down and the semi conductor will let the current through / Forward biased
if no voltage is applied to a semi conductor, what happens?
a depletion zone is formed that has to be overcome before current can flow in the forward-biased direction
0.7V silicon
0.3V germanium
what is the threshold voltage?
the voltage required to breakdown the depletion layer at junctions
0.7V silicon
0.3 Germanium
when a semiconductor diode doesn’t fully block, what happens?
a residual reverse-biased current still flows (Leakage current)
why does a reverse-biased current occur?
caused by residual impurities in the crystal which are broken down by heat waves
what does the amount of residual reverse-biased current depend on?
the type of semiconductor diode type
