SELF-OSCILLATIONS OF DOMAINS IN DOPED GAAS-ALAS SUPERLATTICES

Self-sustained oscillations of the current have been observed and simu lated in a doped GaAs-AlAs superlattice under voltage control. Dependi ng on the applied bias the detected frequencies vary between 250 kHz a t low voltages and 20 MHz at high voltages. Amplitude and frequency de crease with increasing carrier density until, at very high excitation densities, stable electric-field domains are formed. A discrete drift model reproduces the current oscillations and shows that they can be a ttributed to the spatial oscillation of the boundary between the two d omains.