Transferred Electron Amplifiers and Oscillators

TLDR

Some semiconductors have two conduction band minima close in energy, with the lower minimum having a smaller electron effective mass than the upper minimum. The authors propose that at high electric fields electrons can be transferred to the upper minimum, where they exhibit lower mobility. They analyze the conditions for negative resistance and perform calculations for GaSb and semi‑insulating GaAs. Their calculations indicate that conductivity can decrease with increasing field, leading to differential negative resistance that should be observable in both GaSb and semi‑insulating GaAs.

Abstract

In some semiconductors the conduction band system has two minima separated by only a small energy, and the lower minimum has associated with it a smaller electron effective mass than the upper minimum. At high electric fields it should be possible to transfer electrons to the upper minimum where they will have a lower mobility. The conductivity of a homogeneous crystal bar can therefore decrease as the field is increased, and it is conceivable that a differential negative resistance could be obtained. The conditions needed for obtaining negative resistance are examined, and calculations made for GaSb and semi-insulating GaAs. It appears that negative resistances should be observable in both these materials.