We have calculated the resonant tunneling current of electrons in single- and double-barrier GaAs-AlAs heterostructures in the (001) direction. A ten-band empirical tight-binding model is used in which the wave function is propagated through the structure from atom to atom using transfer matrices. We find that electrons generally follow a Γ-Γ-Γ-Γ-Γ or Γ-X-X-X-Γ path through the double-barrier devices, and present curves that show Γ resonances and X resonances as distinct peaks in the transmission coefficient. The tunneling current is calculated and the influence of the different types of resonances is discussed for a double-barrier device. The existence of resonances in the AlAs barriers suggests that negative differential resistance effects can exist in single-barrier devices.
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