Answer: Intervalley transfer from gamma valley (high mobility) to L valley (low mobility), causing NDR.
- A Simple velocity saturation, as seen in ordinary silicon at high fields according to most researchers
- B Intervalley transfer from gamma valley (high mobility) to L valley (low mobility), causing NDR
- C Impact ionization generating additional electron-hole pairs in the majority of cases studied
- D Direct recombination of the conduction electrons with holes as widely reported in standard practice
Correct answer: B. Intervalley transfer from gamma valley (high mobility) to L valley (low mobility), causing NDR
Explanation: Gunn effect: high field transfers electrons from high-mobility central valley to low-mobility satellite valleys. Average velocity decreases. NDR → oscillations.
Conductors have overlapping bands, semiconductors have a small energy gap that can be bridged by heat or doping, and insulators have a large gap that blocks conduction.
Concept context
Band theory, p-n junction, diodes, transistors, logic gates, and integrated circuits.