🔍 Key Concepts

• Gunn effect in semiconductor materials like GaAs (gallium arsenide) • Difference between junction devices (like avalanche / IMPATT diodes) and bulk devices • How negative differential resistance can be used to sustain oscillations

💭 Think About

• Is a Gunn diode based on breakdown of a p-n junction, or on what happens in the body (bulk) of a uniformly doped semiconductor? • Which effect actually causes the diode to behave like a source of microwave oscillations—does it rely on avalanche multiplication, or on regions of negative resistance forming inside the material? • Look at the choices: which terms clearly apply to junction avalanche devices, and which are associated with uniform bulk material under high electric field?

✅ Before You Answer

• Verify whether a Gunn diode even has a p-n junction (this tells you whether avalanche is involved). • Check which term is used to describe devices where the active region is the bulk of the semiconductor rather than a junction. • Confirm that Gunn diodes are classic examples of devices that exhibit negative differential resistance at microwave frequencies.