Compound semiconductors

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?

  1. ABridge rectifier
  2. BDarlington connection
  3. CCascode configuration
Show answer and explanation

Answer: C. Cascode configuration

In the cascode configuration, a low-voltage silicon MOSFET is placed in series on the source side of the GaN HEMT, and the HEMT's gate is tied to the MOSFET's source. Turning off the MOSFET automatically turns off the HEMT, so the combination behaves as a normally-off device. Another advantage is that gate drivers for silicon MOSFETs can be used as is.

  • A. A bridge rectifier converts AC to DC.
  • B. A Darlington connection uses two bipolar transistors to increase current gain.
  • C. Correct. Placing it in series with a Si MOSFET gives normally-off operation.
Practice this topic Back to topic

More Compound semiconductors questions

  1. 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?
  2. 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?
  3. Which correctly describes a "type I" band alignment at a heterojunction?
  4. Why does Mg-doped GaN grown by MOCVD remain highly resistive rather than p-type right after growth, and what is the countermeasure?
  5. What is the phenomenon called in which the efficiency of an InGaN LED actually decreases as the current is increased?