New formation mechanism of electric field domain due to Γ-X sequential tunneling in GaAs/AlAs superlattices

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Abstract
We have studied the sequential tunneling of doped weakly coupled GaAs/AlAs superlattices (SLs), whose ground state of the X valley in AlAs layers is designed to be located between the ground state (EΓ1) and the first excited state (EΓ2) of the Γ valley in GaAs wells. The experimental results demonstrate that the high electric field domain in these SLs is attributed to the Γ-X sequential tunneling instead of the usual sequential resonant tunneling between subbands in adjacent wells. Within this kind of high field domain, electrons from the ground state in the GaAs well tunnel to the ground state of the X valley in the nearest AlAs layer, then through very rapid real-space transfer relax from the X valley in the AlAs layer to the ground state of the Γ valley of the next GaAs well.