At room temperature, the region in a PN junction diode where there are no mobile electrons or holes is called __________________.
Depletion region
A PN junction forms where a p-type region (rich in holes) meets an n-type region (rich in free electrons). The moment they are joined, the steep difference in carrier concentration drives diffusion across the boundary.
- Free electrons from the n-side diffuse across and recombine with holes on the p-side.
- Holes from the p-side diffuse across and recombine with electrons on the n-side.
- This recombination sweeps a thin zone straddling the junction clean of mobile charge carriers — it is left with essentially no free electrons or holes.
What remains in this zone are the immobile ionised atoms: negatively charged acceptor ions on the p-side and positively charged donor ions on the n-side. These fixed charges set up a built-in electric field (and the associated barrier potential) that opposes further diffusion and brings the junction to equilibrium. Because it is depleted of mobile carriers, this zone is called the depletion region (also known as the space-charge region), which is the correct choice.
The other options name regions that still contain plenty of mobile carriers. The bulk n-type region has abundant free electrons, and the bulk p-type region has abundant holes, so neither is carrier-free. An ohmic terminal interface is simply the low-resistance metal-to-semiconductor contact used to wire the diode into a circuit; it is deliberately made non-rectifying and is not the carrier-free layer being described.
Similar Questions
Under forward-bias conditions, what is the primary mechanism that creates forward current across a PN junction?
Before breakdown, increasing reverse voltage causes reverse saturation current to __________.
The existence of cut-in voltage in a diode is mainly due to the presence of __________.
What is the main disadvantage of a half-wave rectifier?
Consider an abrupt p-n junction under thermal equilibrium. If the acceptor doping concentration (NA) in the p-region is made significantly larger than the donor doping concentration (ND) in the n-region (i.e., $N_A ≫ N_D$), how is the depletion region physically distributed?
Important Questions from PN Junction
In a p-n junction diode
1. In reverse bias mode the bulk resistance is dominant.
2. The junction impedance is variable.In a MOS transistor, if n+ region is diffused in p-type substrate, the type of pn junction generated towards channel and drain is:
Match the following lists :
List – I List – II a. Abrupt p-n junction i. p+ n+ b. Linearly graded p-n junction ii. p+ n n+ c. Tunnel diode iii. p π(ν) n d. p-i-n diode iv. p+ p n n+ Correct codes are :
Consider the following statements for a p-n junction diode :
(a) It is an active component
(b) Depletion layer width decreases with forward biasing
(c) In the reverse bias case, saturation current increases with increasing temperatureWhich of the statements given above are correct ?
Under forward-bias conditions, what is the primary mechanism that creates forward current across a PN junction?
