LOCALIZATION EFFECTS IN SEMICONDUCTOR SUPERLATTICES

We investigated two novel effects utilizing localization properties of semiconductor superlattices. First, a phenomenon which consists of op tically induced effective mass change due to carrier localization in s emiconductor superlattices is investigated. It is shown that an optica l field can achieve conductivity changes in a manner similar to a de e lectric held. A possible application as a nonabsorbing differential op tical detector/switch is considered. Second, radiative recombination o f the excitonic states in semiconductor superlattices with an applied electric field is studied theoretically. It is shown that when the ele ctron-hole Coulomb interaction energy exceeds the miniband width, a co herent excitonic state is created whose oscillator strength surpasses the oscillator strength of a single quantum well by orders of magnitud e. It is also demonstrated that a small external field can split the c oherent state into isolated well states and thus severely deplete the oscillator strength of the exciton. This opens the possibility of modu lating and switching of superradiance in semiconductor devices.