Observation Of Resonant Tunneling Research Articles

Observation of resonant tunneling through a self-assembled InAs quantum dot layer

We report on the study of resonant tunneling through a self-assembled InAs quantum dot (QD) layer using the following design: The QD layer surrounded by undoped GaAs barriers is clad by two GaInNAs∕GaAs short-period superlattice regions which serve as injector and collector of electrons. A clear observation of three- to zero-dimensional resonant tunneling is presented in electrophotoluminescence measurement results and supported with current-voltage and capacitance-voltage characteristics.

Observation of resonant tunneling through a self-assembled InAs quantum dot layer

Resonant tunneling through a self-assembled InAs quantum dot (QD) layer using a new design is reported: The QD layer surrounded by undoped GaAs barriers is clad by two GaInNAs∕GaAs short period superlattice regions which serve as injector and collector of electrons. Clear observation of three- to zero-dimensional resonant tunneling is presented in electrophotoluminescence measurement results, and supported with current–voltage and capacitance–voltage characteristics.

Observation of resonant tunneling through a quantized state in InP quantum dots in a double-barrier heterostructure

A direct spectroscopic signature associated with the quantized state of the charge carriers in three-dimensionally confined InP quantum dots (QDs) is reported using a ballistic electron emission microscopy (BEEM)/spectroscopy technique. The self-assembled InP QDs are sandwiched in an AlInP double-barrier heterostructure. The excellent nanometer-scale lateral resolution of the BEEM technique is used to investigate the current transport mechanism by the direct injection of electrons into a single quantum dot. The BEEM spectra taken on and off the dot revealed the presence of a localized state at around 0.1±0.02 eV above the ground state.

Observation of resonant tunneling through single self-assembled InAs quantum dots using electrophotoluminescence spectroscopy

The resonant tunneling through single InAs quantum dots embedded in an n-GaAs/i-Al0.38Ga0.62As/n-GaAs diode has been studied by using microscopic electrophotoluminescence spectroscopy. Many sharp luminescence lines which originated from single quantum dots were observed by injecting resonant electrons from the emitter to the dots. Bias dependence of a single luminescence line was investigated. The peak intensity showed triangular dependence which was similar to the current–voltage characteristics of electron resonant tunneling from three dimension to zero dimension. When the bias voltage was increased, the peak energy slightly shifted to a lower energy indicating the existence of Stark effect, and the linewidth slightly increased. The higher the luminescence energy was, the broader the linewidth was. This result agrees with the calculated resonant level width. The lifetime of resonant states was estimated to be 2.4–27 ps for luminescence linewidth of 250–22 μeV.

Development of CdTe/Cd1-xMgxTe Double Barrier, Single Quantum Well Heterostructures for Resonant Tunneling

Since the first observation of resonant tunneling in GaAs/AlGaAs double barrier stuctures [1], the work in this particular field has been almost exclusively confined to III-V material systems [2-5]. Resonant tunneling devices are interesting for high frequency applications. Moreover, they are of considerable interest in basic research [6]. Double barrier stuctures can be used e.g. for the investigation of interface roughness or band discontinuities. In II-VI semiconductors, resonant tunneling through double barrier structures had been reported only in the HgTe/CdTe system [7]. It has been shown that CdMgTe heterostructures can be grown by molecular beam epitaxy (MBE) with a high quality [8]. Varying the Mg concentration, the energy gap can be tuned from 1.5 eV (CdTe) to 3.5 eV (zinc blende MgTe) [9]. The valence band offset CdTe/MgTe was determined to be 0.7 eV [10, 11]. Therefore a very high electron confinement of 1.3 eV can be obtained. Recently quantum Hall effect in modulation doped CdTe/CdMgTe single quantum wells has been observed [12], demonstrating that high mobility twodimensional systems can be fabricated. In optical studies the non-magnetic CdMgTe turned out to be the ideal counterpart for the semimagnetic CdMnTe due to its very similar crystalline and electronic properties [13, 14]. Thus the quateuary system CdMgMnTe provides the unique possibility to alter separately the electronic and magnetic properties in a heterostructure. In addition, this material system is suitable for the fabrication of quantum wires and dots [15]. Photoluminescence intensity from low-dimensional, deep etched stuctures turned

Observation of resonant tunneling through localized continuum states in electron wave interference diodes

A 13 layer aperiodic semiconductor superlattice electron wave interference filter, designed with thin-film optical interference filter techniques by using the analogies between electromagnetic wave propagation in dielectrics and ballistic electron wave propagation in semiconductors, was realized in the GaAs/AlGaAs material system. Current-voltage measurements at 300 and 77 K show negative differential resistance peaks (with peak-to-valley current ratios of 1.25 and 3.9, respectively) that represent observation of tunneling through an above barrier localized quasibound state. We show that electron wave interference devices could compete with resonant tunneling diodes as high frequency oscillators based on dc device characteristics and theoretical subpicosecond tunneling traversal times.

Observation of resonant tunneling at room temperature in GaInP/GaAs/GaInP double-heterojunction bipolar transistor

Negative differential resistance (NDR) has been observed at room temperature in GaInP/GaAs double-heterojunction bipolar transistors (DHBTs). Both the common-emitter and common-base current-voltage characteristics and their magnetic field dependence have been studied to confirm that the observed NDR is due to resonant tunneling. The collector-base voltages at which the collector current resonances occur are calculated and are consistent with the measured values. The devices exhibit an offset voltage of 57 mV and saturation voltage of <or= 2-V, both of which are the lowest reported values for GaInP/GaAs DHBTs. The collector-base breakdown voltage in these DHBTs is 31 V, and its variation with junction temperature is measured and described.<<ETX>>

Observation of resonant tunneling in InSb/AlInSb double-barrier structures

We report the first observation of resonant tunneling in the InSb/AlxIn1−xSb material system. Five samples with InSb quantum well thicknesses ranging from 70 to 110 Å and Al0.5In0.5Sb barrier thicknesses ranging from 22 to 36 Å were grown by molecular beam epitaxy on GaAs(100) substrates at a temperature of 420 °C. The best sample, which had 22-Å-thick barriers and a 110-Å-thick quantum well, displayed a peak-to-valley current ratio of 1.4(3.9) at room temperature (77 K) with a corresponding peak current density of 3.6×104 A/cm2. Transmission electron microscopy revealed threading dislocations, misfit dislocations, and microtwins in the barrier region.

Observation of resonant tunneling through a compositionally graded parabolic quantum well

We report the first observation of electron resonant tunneling through parabolic quantum wells, compositionally graded by means of short-period (15 Å) AlxGa1−xAs/GaAs superlattices grown by molecular beam epitaxy. In one structure, comprising a 300-Å-wide well compositionally graded from AlAs to GaAs, five equally spaced resonances are observed in the current-voltage (I-V) characteristic in good agreement with the theory. In another structure with 432-Å-wide wells graded from Al0.30Ga0.70As to GaAs, up to 16 resonances are observed in the I-V. The first ten correspond to resonant tunneling through the quasi-bound states of the double barrier while the others are ascribed to electron interference effects associated with virtual levels in the quasi-continuum energy range above the collector barrier.

Observation of resonant tunneling through GaAs quantum well states confined by AlAs X-point barriers

Experimental evidence of resonant tunneling via quasistationary states confined by AlAs X-point potential energy barriers is reported in GaAs/AlAs double barrier heterostructures grown in the [100] direction. The quantum well energy levels giving rise to the negative differential resistances observed in the current-voltage characteristics are identified by calculating the energy-band diagrams of the structures. These resonant energy levels correspond to states confined in the GaAs well not only by the AlAs Γ-point potential energy barriers but also by the AlAs X-point barriers. The quasibound X states are associated with the large longitudinal effective mass in AlAs corresponding to the direction perpendicular to the heterojunction interfaces.

Observation of resonant tunneling in silicon inversion layers.

Measurements of the temperature and carrier-density dependence of the strongly localized conductance of short silicon inversion layers are reported. At the lowest temperatures we observe well-isolated, large conductance peaks whose width and temperature dependence are only consistent with resonant tunneling and are inconsistent with Mott hopping. Several new features are observed which we believe may be the result of Coulomb interactions.