JEE Physics - MCQ Practice Questions

Wide bandgap material (AlGaAs) acts as barrier, confining carriers to narrow bandgap GaAs region. This reduces recombination, improves injection efficiency, and is crucial for LEDs and laser diodes.

Higher doping concentrations create stronger electric fields at lower voltages, reducing Zener breakdown voltage. This allows designing Zeners with specific breakdown voltages (3.3V, 5.1V, etc.).

At low forward bias, electrons tunnel through the narrow bandgap, creating peak current. As voltage increases, direct band-to-band current dominates, causing current to decrease with voltage (negative differential resistance).

The process transconductance parameter k_n = μ_n × C_ox determines how efficiently the MOSFET converts gate voltage to drain current. Both μ_n and C_ox are independent device parameters.

FinFETs employ multiple gates (typically 3 gates) wrapping around a thin silicon fin, providing superior electrostatic control of the channel, reducing short-channel effects and subthreshold swing.

Due to lower hole mobility in PMOS (~2-3 times lower than electron mobility in NMOS), the PMOS width must be 2-3 times larger to match switching speeds and minimize inverter delay.

The Early effect occurs because increased reverse bias widens the depletion region, reducing the effective base width. This decreases recombination in the base and increases collector current. The Early voltage V_A is inversely proportional to base doping concentration.