Inelastic tunneling characteristics of AlAs/GaAs heterojunctions

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Abstract
We report the first observation of inelastic tunneling in electronic transport perpendicular to a thin AlAs layer sandwiched between two GaAs layers. Temperature dependent I–V, first derivative (dI/dV), and second derivative (d2I/dV2) measurements were made on AlAs/GaAs double heterojunctions for a range of AlAs layer thicknesses and dopings. For p-type AlAs barriers current transport at 4.2 K was due to tunneling, and reproducible structure was seen in the second derivative spectrum. This structure was associated with the inelastic excitation of AlAs optical phonons and with a density-of-states effect caused by optical phonon-electron coupling in the GaAs. A different second derivative spectrum which also exhibited reproducible structure was obtained for n-type AlAs layers. Several possible explanations for these differences are proposed.