SELF-OSCILLATIONS OF THE CURRENT IN DOPED SEMICONDUCTOR SUPERLATTICES

Self-sustained current oscillations have been found in doped GaAs-AlAs superlattices and are investigated experimentally and theoretically, The electric-field distribution in doped superlattices becomes unstabl e if the carrier density is not sufficiently large to form stable doma ins. The instability results in self-oscillations of the current, whic h are due to an oscillatory motion of the domain boundary in the super lattice. A discrete drift model taking into account several regions of negative differential velocity and a large electron density clearly e stablishes the origin of these oscillations.