LOCALIZATION EFFECTS IN SEMICONDUCTOR SUPERLATTICES

We investigated two novel effects utilizing localization properties of semiconductor super-lattices. First, a phenomenon which consists of optically induced effective mass change due to carrier localization in semiconductor superlattices is investigated. It is shown that an optical field can achieve conductivity changes in a manner similar to a dc electric field. A possible application as a nonabsorbing differential optical detector/switch is considered. Second, radiative recombination of the excitonic states in semiconductor superlattices with an applied electric field is studied theoretically. It is shown that when the electron-hole Coulomb interaction energy exceeds the miniband width, a coherent excitonic state is created whose oscillator strength surpasses the oscillator strength of a single quantum well by orders of magnitude. It is also demonstrated that a small external field can split the coherent state into isolated well states and thus severely deplete the oscillator strength of the exciton. This opens the possibility of modulating and switching of superradiance in semiconductor devices.