Which of the following is a transferred-electron device (TED) used for microwave generation and amplification?

Introduction:
Transferred-electron devices (TEDs) exploit negative differential resistance arising from electron transfer between energy valleys in certain semiconductors. This question checks whether you can identify which microwave diode operates on the Gunn effect.

Given Data / Assumptions:

• Common microwave diodes: Gunn, IMPATT, BARITT, step-recovery, tunnel.
• TED behavior involves intervalley electron transfer under high electric fields.

Concept / Approach:

The Gunn diode is the archetypal TED, typically fabricated in GaAs or InP. When biased above a threshold field, it exhibits negative differential resistance and can oscillate at microwave frequencies without a pn junction.

Step-by-Step Solution:

Verification / Alternative check:

Frequency–field domain formation in Gunn devices (transit-time domains) is the hallmark of TED operation, absent in the other listed diodes.

Why Other Options Are Wrong:

• IMPATT/BARITT: rely on impact ionization or barrier injection and transit-time effects, not TED behavior.
• Step-recovery diode: used for pulse sharpening/harmonics via charge storage.
• Tunnel diode: quantum tunneling device with its own negative resistance mechanism, not TED.

Common Pitfalls:

Confusing all negative-resistance devices as TEDs. Only Gunn devices specifically use transferred-electron physics.

Final Answer:

Gunn diode