P. Guéret

Investigations on resonant tunneling in III‐V heterostructures

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.

Experimental observation of the dynamical image potential in extremely low GaAs/AlxGa1−xAs/GaAs tunnel barriers

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.

Investigation of possible dynamic polarization effects on the transmission probability of n-GaAs/AlxGa1−xAs/n-GaAs tunnel barriers

Abstract Tunneling through n-GaAs/AlxGa1−xAs/n-GaAs barriers has been systematically investigated over a wide range of barrier heights and thicknesses (up to 100 nm). This study provides experimental evidence that an electron sees a dynamically variable potential barrier as it tunnels through. The general form of this potential is inferred from the data, and its relation to the tunneling time of Buttiker and Landauer discussed.

Investigations on resonant tunneling in III‐V heterostructures: Comparison between experimental data and model calculations

Data obtained on a set of GaAs/AlGaAs double‐barrier quantum‐well resonant tunneling structures are compared with model calculations of the ideal case where scattering is negligible and tunneling is coherent throughout the entire structure. The comparison points to interface roughness in the well as the most likely cause for the observed large valley currents. The currents at low biases, before resonance sets in, are also studied. Their magnitude is found to be consistent also with the sequential tunneling picture.

Resistance of very small area ohmic contacts on GaAs

Very small area, alloyed ohmic contacts on n+‐GaAs etched mesas have been fabricated and their resistance measured. The nominal contact size ranges from 10 down to 0.1 μm on a side. The data show an extremely large increase of the resistance spread as the contact size is reduced. Grain size effects in the alloyed contacts and dead zones due to ion etching are discussed as possible causes for the observations.

Conductance statistics of small‐area ohmic contacts on GaAs

The conductance distributions of very small‐area alloyed ohmic contacts on n+‐GaAs have been studied as a function of lateral contact size d, with d ranging from 4 μm down to 0.3 μm. The data are fairly well represented by a Poisson distribution, which takes into account the granularity of the alloyed contacts, as previously reported. We deduce an average distance of dc ≂0.41 μm between conducting grains and a dead zone of ld ≂600 A due to dry etching of the GaAs.

Tunneling through asymmetric double‐barrier quantum‐well heterostructures

Data obtained from a set of asymmetric GaAs/AlGaAs double‐barrier resonant tunneling structures is presented. Low‐temperature I(V) characteristics, temperature dependencies, and magnetotunneling have been investigated. The data confirm conclusions drawn in previous studies on symmetric structures, lending further support to the description of tunneling in terms of sequential processes and momentum randomization most likely induced by interface roughness scattering in the well.

Tunneling Through III–V Low-Barrier Heterostructures

This paper deals with tunnelling through very low and thick Al x Ga 1−x As barriers. E xperimental results are presented and compared with theory. Measurements in a transverse magnetic field are also described, and their relationship to the tunnelling time discussed. They provide further confirmation of direct, “ballistic” tunnelling through thick barriers.

Is the momentum of a tunneling electron real or imaginary? An alternative description of the tunneling process

The momentum of a tunneling electron is real if its rest mass in the barrier acts as a reservoir which can trade rest energy for kinetic energy in accordance with special relativity. The Buttiker-Landauer expression for the tunneling time follows directly from this thermodynamic picture.