Semiconductors Knowledge-Based Practice

Questions

1. 1.

   Which of the following binary materials is classified as a III-V compound semiconductor commonly utilized in optoelectronic and high-frequency electronic devices?

   • A) Cadmium sulfide (CdS)
   • B) Zinc selenide (ZnSe)
   • C) Silicon carbide (SiC)
   • D) Indium phosphide (InP)
2. 2.

   When an abrupt p-n junction is formed between p-type and n-type semiconductor regions in the absence of an applied voltage, which process accounts for the establishment of the depletion region?

   • A) Continuous drift of minority carriers driven by external magnetic fields until thermal equilibrium is established.
   • B) Direct chemical reaction between acceptor and donor dopant nuclei across the interface forming an amorphous barrier layer.
   • C) Diffusion of majority carriers across the interface followed by mutual recombination, leaving behind immobile, ionized dopant atoms.
   • D) Complete migration of all dopant ions from the interface toward the outer terminal contacts by electrostatic repulsion.
3. 3.

   When an intrinsic elemental semiconductor such as pure germanium is doped with a trivalent element such as gallium, which majority charge carrier and energetic mechanism are primarily responsible for the resulting electrical conductivity?

   • A) Excess conduction-band electrons generated from discrete donor energy levels located just below the conduction band
   • B) Thermally generated intrinsic electron-hole pairs created across an unaltered fundamental bandgap
   • C) Positive holes in the valence band created when valence electrons are accepted into shallow energy levels near the valence band
   • D) Mobile ionic vacancies within the crystal lattice that permit the direct migration of localized negative charges
4. 4.

   Which of the following statements correctly describes how increasing temperature affects the electrical conductivity of an intrinsic semiconductor, along with the underlying physical cause?

   • A) Conductivity decreases because enhanced lattice vibrations significantly increase carrier scattering.
   • B) Conductivity decreases because thermal expansion widens the band gap between the valence and conduction bands.
   • C) Conductivity increases because thermal excitation promotes more electrons from the valence band into the conduction band.
   • D) Conductivity remains unchanged because thermal energy is insufficient to alter carrier concentrations in intrinsic crystals.
5. 5.

   Which of the following dopants, when incorporated into an intrinsic silicon crystal lattice, produces an n-type semiconductor by contributing donor electrons?

   • A) Boron
   • B) Gallium
   • C) Indium
   • D) Phosphorus

Answers and step-by-step solutions appear after you finish the test.