Compound semiconductors

Learn the features of compound semiconductors such as GaAs, GaN and InP, and the difference between direct and indirect band gaps, through multiple-choice questions.

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Compound semiconductors: key points

Compound semiconductors are made of more than one element, such as GaAs (gallium arsenide) and GaN (gallium nitride). Combinations of group III and group V elements (III-V) are typical.

Some have higher electron mobility than silicon, some have direct band gaps that emit light efficiently, and some have large band gaps. They are used in high-frequency devices, LEDs and lasers, and power devices.

All Compound semiconductors questions (50)

  1. What type of band structure does gallium arsenide (GaAs) have?
  2. Which is classified as a III-V compound semiconductor?
  3. What is the main reason GaAs has been used in RF amplifiers for mobile phones and similar applications?
  4. What are InP (indium phosphide)-based compound semiconductors mainly used for?
  5. Which material is mainly used in the light-emitting layer of blue LEDs?
  6. What is an advantage of alloy semiconductors such as AlGaAs?
  7. What is a typical application of HEMTs (high electron mobility transistors)?
  8. In GaN devices, which substrates are commonly used for growing the GaN layers?
  9. Which is a characteristic of gallium oxide (Ga2O3), under research as a next-generation power semiconductor material?
  10. What is the approximate wavelength of light emitted by GaAs, which has a band gap of about 1.42 eV?
  11. Which correctly describes the typical diameter of wafers for compound semiconductors such as GaAs?
  12. Which is a typical material for high-brightness red to yellow LEDs?
  13. Which correctly describes the quantum well structure used in the light-emitting layers of semiconductor lasers and LEDs?
  14. Which is a characteristic of a VCSEL (vertical-cavity surface-emitting laser)?
  15. Why is care needed when handling GaAs wafer processing debris and waste?
  16. Why is GaN well suited to high-frequency, high-power transistors?
  17. What is one main reason SiC is used as the substrate for GaN HEMTs?
  18. Which material is mainly used in the light-emitting layer of deep-ultraviolet LEDs, such as those for sterilization?
  19. Which is a characteristic of multi-junction solar cells, which stack several compound semiconductor layers with different band gaps?
  20. Which impurity is typically used to make p-type layers in GaN?
  21. What is the typical crystal structure of GaN?
  22. Which is an example of an application of HBTs (heterojunction bipolar transistors) made from InP or GaAs?
  23. When silicon is added to GaAs to make it n-type, which site does the silicon mainly occupy?
  24. What is the advantage of using semi-insulating GaAs substrates for GaAs RF ICs?
  25. Which is a characteristic of micro-LED displays?
  26. What structure do most of today's widely used GaN power devices adopt?
  27. Which is a characteristic of diamond, sometimes called the ultimate semiconductor material?
  28. How does the thermal conductivity of GaAs compare with that of silicon?
  29. What is the advantage of growing InGaAs, with its composition adjusted, lattice-matched on an InP substrate?
  30. In silicon photonics, why are compound semiconductors combined with silicon for the laser light source?
  31. Which trio of researchers received the 2014 Nobel Prize in Physics for inventing the high-brightness blue LED?
  32. Which elements make up gallium arsenide (GaAs)?
  33. Why is LED lighting more energy-efficient than incandescent bulbs?
  34. Which compound semiconductor, with very high electron mobility, is used in magnetic sensors (Hall elements) and the like?
  35. What is the gate structure of the MESFET, long used as a high-frequency GaAs transistor?
  36. Which material, named for its crystal structure, has attracted intense research as a high-efficiency solar cell material that can be made by low-temperature processes such as coating?
  37. In LEDs with an InGaN emitting layer, how does the emission color change when the indium (In) fraction is increased?
  38. What material is used for the blue-violet semiconductor laser of about 405 nm that reads and writes Blu-ray discs?
  39. Which material, whose band gap can be tuned by composition, has been used for high-performance mid- to long-wave infrared detectors?
  40. Which is one reason it is difficult to build silicon-like CMOS circuits in GaAs?
  41. How is silicon germanium (SiGe) classified?
  42. What is a high-frequency IC called that integrates transistors together with passive components such as inductors and capacitors on a substrate such as GaAs?
  43. What is the empirical rule called that says the lattice constant of an alloy semiconductor such as AlGaAs varies almost linearly with composition?
  44. Which configuration combines a normally-on GaN HEMT in series with a low-voltage silicon MOSFET so it can be used safely with normally-off behavior?
  45. When a strong field is applied to GaAs, electrons transfer to another valley with lower mobility, and negative differential resistance appears in which current decreases as the field rises. Which oscillator device uses this?
  46. What is the problem called in which LED external quantum efficiency is high for blue (InGaN) and red (AlGaInP) but low in the green-to-yellow range between them?
  47. Which correctly describes a "type I" band alignment at a heterojunction?
  48. Why does Mg-doped GaN grown by MOCVD remain highly resistive rather than p-type right after growth, and what is the countermeasure?
  49. What is the phenomenon called in which the efficiency of an InGaN LED actually decreases as the current is increased?
  50. What does LED stand for?

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