Resonant Tunneling in Double Barrier Heterostructures
Semiconductor quantum wells are the subject of considerable interest due to the ability to confine carriers in ultrathin (<100Å) semiconductor layers bounded by lower electron affinity (higher bandgap) potential barriers. When the dimension of the thin lower bandgap layer approaches the carrier mean free path, the restriction of the carrier motion in the direction perpendicular to the layer interface causes electric quantization that govern the electronic and optical properties. The formation of these quantum states (subbands) in the thin layer (“quantum well”) confined by thick barriers allows for the experimental investigation of quasi-two dimensional carriers. In the case that the barriers are sufficiently thin such that the quantum well states are quasi-bound (due to quantum mechanical tunneling through the barrier), then it is possible to directly probe the electronic structure of the quantum well by carrier transport through the structure. This phenomena of resonantly tunneling through these quantum well states was first experimentally realized by Chang, Esaki, and Tsu1 in a GaAs quantum well / AlGaAs double barrier heterostructure. Recent advances in advanced semiconductor epitaxy, typified by molecular beam epitaxy (MBE) in the GaAs/AlGaAs system, has generated remarkable interest and success in these investigations.2–7
KeywordsResonant Tunneling Negative Differential Resistance Double Barrier Central Quantum Double Barrier Structure
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