Properties of Electrical Materials – Medium Difficulty
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#1. What is the typical bandgap energy of silicon at room temperature?
#2. In an intrinsic semiconductor at thermal equilibrium, which statement is true?
#3. What type of semiconductor is created when silicon is doped with phosphorus?
#4. What type of semiconductor is created when silicon is doped with boron?
#5. The Fermi level in an n-type semiconductor at room temperature is located:
#6. The Fermi level in a p-type semiconductor at room temperature is located:
#7. What is the intrinsic carrier concentration of silicon at room temperature (300K)?
#8. Which of the following is a direct bandgap semiconductor?
#9. In a semiconductor, what happens to the bandgap energy as temperature increases?
#10. What is the primary difference between a conductor and a semiconductor in terms of band structure?
#11. Drift current in a semiconductor is caused by:
#12. Diffusion current in a semiconductor is caused by:
#13. The Einstein relation connects which two parameters?
#14. At room temperature (300K), the thermal voltage (kT/q) is approximately:
#15. Which carrier has higher mobility in silicon at room temperature?
#16. The total current density in a semiconductor is given by:
#17. If the electron mobility in silicon is 1350 cm²/V·s and an electric field of 100 V/cm is applied, what is the electron drift velocity?
#18. What happens to carrier mobility as temperature increases in a semiconductor?
#19. What happens to carrier mobility as doping concentration increases significantly?
#20. The diffusion coefficient for electrons in silicon at room temperature is approximately 35 cm²/s. Using the Einstein relation, what is the electron mobility?
#21. What is the built-in potential of a silicon p-n junction at room temperature if NA = 10^17 cm^-3 and ND = 10^16 cm^-3?
#22. In a p-n junction at equilibrium (no applied voltage), the net current is:
#23. When a p-n junction is forward biased, the depletion region:
#24. When a p-n junction is reverse biased, the depletion region:
#25. The depletion region in a p-n junction contains primarily:
#26. In an abrupt p-n junction, if the n-side is more heavily doped than the p-side, the depletion region extends:
#27. The reverse saturation current of a p-n junction diode:
#28. The ideal diode equation is I = Is(e^(V/nVT) – 1). What does the ideality factor ‘n’ typically equal for an ideal diode?
#29. What is the primary mechanism of current flow in a forward-biased p-n junction?
#30. The junction capacitance of a reverse-biased p-n junction:
#31. Quantum tunneling in semiconductors occurs when:
#32. In a Zener diode operating in breakdown, which mechanism dominates at lower breakdown voltages (< 5V)?
#33. The tunneling probability through a barrier depends on:
#34. In a tunnel diode, the negative differential resistance region occurs because:
#35. Which type of diode utilizes quantum tunneling as its primary operating mechanism?
#36. The electrical conductivity of a semiconductor is given by:
#37. What is the relationship between conductivity (σ) and resistivity (ρ)?
#38. A silicon sample is doped with 10^16 cm^-3 donors. If electron mobility is 1200 cm²/V·s, what is the approximate resistivity?
#39. Which material has the highest electrical conductivity at room temperature?
#40. The resistivity of a metal typically:
#41. The resistivity of a semiconductor typically:
#42. What is the typical resistivity range for intrinsic silicon at room temperature?
#43. Sheet resistance (Rs) is defined as:
#44. A thin film has a sheet resistance of 100 Ω/square. If a resistor pattern is 5 squares long and 2 squares wide, what is the total resistance?
#45. The temperature coefficient of resistance for copper is approximately:
#46. The relative permittivity (dielectric constant) of silicon is approximately:
#47. The permittivity of free space (ε0) is approximately:
#48. The absolute permittivity of a material is calculated as:
#49. A parallel plate capacitor has a capacitance of 100 pF with air as the dielectric. If the air is replaced with a material having εr = 4, the new capacitance is:
#50. Which of the following materials has the highest dielectric constant?
#51. The dielectric strength of a material refers to:
#52. The dielectric constant of silicon dioxide (SiO2) is approximately:
#53. In a MOS capacitor, using a high-k dielectric instead of SiO2 allows:
#54. The permeability of free space (μ0) is:
#55. A ferromagnetic material has a relative permeability (μr) of:
#56. A diamagnetic material has a relative permeability (μr):
#57. A paramagnetic material has a relative permeability (μr):
#58. The inductance of a coil with a ferromagnetic core compared to an air core is:
#59. The B-H curve of a ferromagnetic material shows:
#60. The area enclosed by a B-H hysteresis loop represents:
#61. Soft magnetic materials are characterized by:
#62. Hard magnetic materials are characterized by:
#63. The Curie temperature is the temperature above which:
#64. Thermal noise (Johnson-Nyquist noise) in a resistor is caused by:
#65. The thermal noise voltage across a resistor is given by Vn = √(4kTRB). What does B represent?
#66. Shot noise is associated with:
#67. Flicker noise (1/f noise) is characterized by:
#68. Which type of noise dominates at very low frequencies in semiconductor devices?
#69. The noise figure of an amplifier is defined as:
#70. A resistor at 300K with R = 10 kΩ and bandwidth of 1 MHz has a thermal noise voltage of approximately:
#71. To reduce thermal noise in a circuit, one can:
#72. The shot noise current in a diode is given by In = √(2qIdcB). If Idc = 1 mA and B = 1 MHz, the shot noise current is approximately:
#73. Avalanche noise occurs in:
#74. Which metal has the highest thermal conductivity at room temperature?
#75. The thermal conductivity of silicon at room temperature is approximately:
#76. The thermal conductivity of silicon dioxide (SiO2) is approximately:
#77. The Wiedemann-Franz law relates:
#78. In metals, heat is primarily conducted by:
#79. In insulators and semiconductors, heat is primarily conducted by:
#80. The thermal resistance of a material layer is given by:
#81. Diamond has an exceptionally high thermal conductivity (up to 2000 W/m·K) because:
#82. The junction temperature of a semiconductor device can be calculated using:
#83. A transistor dissipates 5W and has a junction-to-ambient thermal resistance of 40°C/W. If the ambient temperature is 25°C, the junction temperature is:
#84. The coefficient of thermal expansion (CTE) of silicon is approximately:
#85. Thermal expansion mismatch between materials in electronic packages can cause:
#86. The linear thermal expansion of a material is given by:
#87. A copper trace is 10 cm long at 25°C. If heated to 125°C, how much does it expand? (α = 17 × 10^-6 /°C)
#88. Which material is often used as a substrate in electronic packages due to its CTE being close to silicon?
#89. The volumetric coefficient of thermal expansion is approximately:
#90. Invar is an alloy known for its:
#91. Thermal stress in a constrained material due to temperature change is given by:
#92. A silicon die (CTE = 2.6 ppm/°C) is mounted on a copper leadframe (CTE = 17 ppm/°C). During a 100°C temperature change, the CTE mismatch is:
#93. To minimize thermal stress in electronic assemblies, one should:
#94. The mass action law for semiconductors states that:
#95. In a heavily doped n-type semiconductor, the minority carrier concentration is:
#96. The depletion approximation assumes that:
#97. The breakdown voltage of a p-n junction increases with:
#98. The minority carrier lifetime in a semiconductor is:
#99. The diffusion length of minority carriers is given by:
#100. Generation-recombination in semiconductors refers to:
