Compound semiconductors

In LEDs with an InGaN emitting layer, how does the emission color change when the indium (In) fraction is increased?

  1. AIt does not change
  2. BToward ultraviolet (shorter wavelength)
  3. CToward longer wavelengths (from blue to green)
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Answer: C. Toward longer wavelengths (from blue to green)

InN has a smaller band gap than GaN, so increasing the In fraction of InGaN narrows the band gap and lengthens the emission wavelength. A lower In fraction gives blue emission and a higher one gives green. However, high In fractions make it difficult to maintain crystal quality.

  • A. The band gap changes with composition, so the color changes too.
  • B. Moving toward UV requires widening the band gap, for example by adding Al.
  • C. Correct. The band gap shrinks and the wavelength lengthens.
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More Compound semiconductors questions

  1. What material is used for the blue-violet semiconductor laser of about 405 nm that reads and writes Blu-ray discs?
  2. Which material, whose band gap can be tuned by composition, has been used for high-performance mid- to long-wave infrared detectors?
  3. Which is one reason it is difficult to build silicon-like CMOS circuits in GaAs?
  4. How is silicon germanium (SiGe) classified?
  5. 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?