Govt. Exams
Entrance Exams
Maximum power point (MPP) occurs at the knee of the I-V characteristic where the product V×I is maximum, typically at ~80% of Voc and ~90% of Isc.
Reverse bias widens the depletion region, allowing photogenerated carriers throughout this region to be swept out by the electric field, improving collection efficiency and response time.
More negative Vgs increases the reverse bias on the gate junction, expanding the depletion region and narrowing the conducting channel, thus decreasing conductance.
Diffusion length Ln = √(Dn·τn) where Dn is diffusion coefficient and τn is minority carrier lifetime. It represents the average distance a carrier travels before recombination.
Direct bandgap semiconductors like GaAs allow radiative recombination (photon emission) without phonon assistance, making them ideal for LEDs and lasers.
Zener breakdown (sharp, reversible breakdown at lower voltages) occurs when a strong electric field in the depletion region enables direct tunneling of electrons across the narrow bandgap.
I₀ ∝ ni² which increases exponentially with temperature. This thermal generation of minority carriers in the neutral regions near the junction constitutes the reverse saturation current.
Using mass action law: ne·nh = ni². Since ne ≈ Nd = 10^16 cm^-3, then nh = ni²/ne = (1.5×10^10)²/10^16 = 2.25×10^4 cm^-3
Increasing reverse bias voltage creates a stronger electric field, pushing charge carriers away from the junction and widening the depletion region according to W ∝ √V.
Though mobility decreases with temperature (T^-3/2), the exponential increase in carrier concentration (proportional to exp(-Eg/2kT)) dominates, resulting in net increase in conductivity.
