Semiconductor Flashcards
What is the forbidden energy gap ?
The forbidden energy gap, or band gap, is the energy difference between the highest energy level of the valence band and the lowest energy level of the conduction band in a semiconductor or insulator.
What is the forbidden energy gap for conductors, insulators and semiconductors ?
Conductor : ~ 0eV
Insulator : >3eV
Semiconductor : <3eV
What is the reason for the current in semiconductor ?
Electron and holes
What is the value of the forbidden energy gap for silicon and germanium ?
Si = 1.1eV
Ge = 0.7eV
How does semiconductor behave at zero kelvin and at room temperature ?
At zero kelvin semiconductors behave as insulators.
At room temperature, some electrons gain energy and jump from the valence band to the conduction band. As a result, the valence band becomes partially empty and the conduction band becomes partially filled.
What is the difference between intrinsic and extrinsic type of semiconductor ?
Intrinsic semiconductors are pure forms of semiconductors. Extrinsic semiconductors are doped to increase their conductivity.
What type of impurity is added to n-type and p-type semiconductors?
In N-type semiconductors, pentavalent impurities like phosphorus (P), arsenic (As), and antimony (Sb) are added (donor impurities). In P-type semiconductors, trivalent impurities like boron (B), aluminum (Al), and indium (In) are added (acceptor impurities).
What is the charge on N type and P type of semiconductor ?
Entirely neutral
What is the reason for current flow in N-type semiconductors and current flow in P-type semiconductors?
In N-type semiconductors, current flows mainly due to electrons, while in P-type semiconductors, it flows mainly due to holes.
What is the diffusion current and drift current in the PN junction ?
Diffusion current is caused by the movement of majority carriers and therefore flows from the p-side to the n-side; this is also called forward current. Drift current, on the other hand, is caused by the movement of minority carriers and thus flows from the n-side to the p-side; it is also known as reverse current.
What is the total current if there is no biasing in a PN junction?
If there is no biasing then diffusion current is equal to drift current. So total current is zero.
In PN junction which side is at high potential ?
N side is at high potential relative to the P side.
What is the average value for barrier potential in PN junction ?
0.5 Volt
What is the relationship between the thickness of the depletion region, doping, and temperature?
The thickness of the depletion region is inversely proportional to both doping concentration and temperature.
