Compound semiconductors

Which correctly describes a "type I" band alignment at a heterojunction?

  1. AThe conduction band minimum and valence band maximum of the narrower-gap material both lie within the band gap of the wider-gap material
  2. BThe band gaps of the two materials do not overlap
  3. CThe conduction and valence bands of the two materials are offset in a staggered way
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Answer: A. The conduction band minimum and valence band maximum of the narrower-gap material both lie within the band gap of the wider-gap material

In type I alignment, the bands of the narrower-gap material lie inside those of the wider-gap material, so both electrons and holes are confined in the narrow-gap layer. This is used in LED and laser quantum wells for efficient recombination. A staggered alignment is type II.

  • A. Correct. Both electrons and holes are confined in the same layer.
  • B. A completely non-overlapping alignment is called type III.
  • C. A staggered alignment is type II.
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More Compound semiconductors questions

  1. Why does Mg-doped GaN grown by MOCVD remain highly resistive rather than p-type right after growth, and what is the countermeasure?
  2. What is the phenomenon called in which the efficiency of an InGaN LED actually decreases as the current is increased?
  3. What does LED stand for?
  4. What type of band structure does gallium arsenide (GaAs) have?
  5. Which is classified as a III-V compound semiconductor?