Tunneling in low-barrier GaAs/AlxGa1−xAs/GaAs heterostructures has been systematically investigated over a wide range of barrier heights and thicknesses. Measured conductance data have been compared with tunnel conductances calculated with and without the image potential correction. Experimental evidence is found for the validity of the static image correction in the limit of large tunneling times, and for the occurrence of dynamic effects in the limit of short tunneling times.
We present data obtained on a set of symmetric GaAs/AlGaAs double-barrier quantum-well structures in which the thickness of the AlGaAs barriers has been systematically varied from 31 to 7.5 nm. Low-temperature I(V ) characteristics, temperature dependencies, and magnetotunneling have been investigated. Our data suggest a dominance of sequential tunneling processes in the range investigated and point to interface roughness in the well as the possible cause for the large valley currents. Our best devices exhibit a current peak-to-valley ratio of about 20.
The influence of a transverse magnetic field on tunnelling through GaAs/A1,Gal-,As/GaAs heterostructures is investigated theoretically and experimentally. The effect is quite significant for the very thick and low barriers studied. I t provides a simple way to determine the barrier transversal time introduced by Stevens, as well as Buttiker and Landauer, from a purely static measurement.
We present calculations and measurements of current as a function of voltage I(V), and conductivity at low voltage as a function of temperature, G(T), for n+ -GaAs/i- Alx Ga1−x As/n+ -GaAs single-barrier tunneling structures. The current is modeled by its tunneling and thermionic emission components. The shape of the conduction-band edge is obtained by solving Poisson’s equation self-consistently, together with two different models for the charge density. In the first model, the electron density is evaluated semiclassically, and in the second, the electron density is calculated from the electronic wave functions. Good agreement is obtained with both models between the experimental and the calculated I(V) and G(T) characteristics over the 4.2–200 K temperature range. The fits obtained are very sensitive to small variations (1%) in barrier width and effective barrier height, which allows one to determine these parameters within a narrower uncertainty range.
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