Evidence of strong phonon-assisted resonant intervalley up-transfer for electrons in type-II GaAs-AlAs superlattices

We demonstrate that interface optical phonons can efficiently pump electrons from the quasi-X states to the quasi-T states in short-period type-II GaAs-AlAs superlattices. As a result, peculiar behaviors on these superlattices have been observed. First, photoluminescence intensity for the quasi-direct transition drastically increases as the temperature or pump power increases. Second, the dependence of the integrated photoluminescence intensity on the pump power exhibits a square power law.