Electric-field domains in semiconductor superlattices: Resonant and nonresonant tunneling

Photoluminescence experiments detecting the occupation of higher subbands in GaAs-Alₓ{Ga}_{1{{-}}x}$As superlattices are used to determine the field strengths of electric-field domains. While the magnitude of the electric field in the low-field domain corresponds to resonant alignment of subbands in adjacent wells, the field strength in the high-field domain is below the value corresponding to the resonant field. These results are interpreted in terms of a simple model based on current conservation.