Transport characteristics of L-point and Г-point electrons through GaAs-Ga_(1-x)Ai_xAs-GaAs(111} double heterojunctions

Abstract

We present here a study on the transport characteristics of L‐point and Γ‐point derived electrons through abrupt GaAs–Ga_(1−x)Al_xAs–GaAs(111) double heterojunctions. The use of complex‐k band structures in the tight‐binding approximation and transfer matrices provide a reasonably accurate description of the wave function at the GaAs–Ga_(1−x)Al_xAs interface. A representation of the wave function in terms of bulk complex‐k Bloch states is used in the GaAs regions where the potential is bulklike. A representation of the wave function in terms of planar orbitals is used in the central Ga_(1−x)Al_xAs region where the potential deviates from its bulk value (i.e., interfacial region). Within this theoretical framework, realistic band structure effects are taken into account and no artificial rules regarding the connection of the wave function across the interface are introduced. The ten‐band tight‐binding model includes admixture in the total wave function of states derived from different extrema of the GaAs conduction band. States derived from the same extremum of the conduction band appear to couple strongly to each other, whereas states derived from different extrema are found to couple weakly. Transport characteristics of incoming L‐point and Γ‐point Bloch states are examined as a function of the energy of the incoming state, thickness of the Ga_(1−x)Al_xAs barrier, and alloy composition x. Transmission through the Ga_(1−x)Al_xAs barrier is either tunneling or propagating depending on the nature of the Bloch states available for strong coupling in the alloy. Since Bloch states derived from different extrema of the conduction band appear to couple weakly to each other, it seems possible to reflect the low velocity L‐point component of the current while transmitting the high velocity Γ‐point component.

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