AMPLIFICATION OF PLASMA MODES IN SEMICONDUCTOR HETEROSTRUCTURES

We investigate current driven instabilities of plasma modes in semiconductor heterostructures. Amplification of the plasma modes becomes possible when electrons are driven parallel to the interface by a sufficiently large electric field. Effects of electron-electron and electron-phonon scatterings are included. We find that the idealized, strictly two-dimensional treatment of the charge carriers used in our previous studies is an excellent approximation if only one subband is occupied at T = 0, and the frequency of the generated oscillation is much less than the intersubband separation. We also find that if more subbands are occupied, the threshold drift velocity for this instability can be significantly reduced, making it more practical for device applications.