Magneto-optical investigation of two-dimensional gases in n-type resonant tunneling diodes (original) (raw)
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Spin injection in n-type resonant tunneling diodes
Nanoscale Research Letters, 2012
We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X − ). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to −88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.
Journal of Physics D: Applied Physics, 2013
In this work, we have investigated the spin polarization from two-dimensional hole gases (2DHG) formed in p-i-p GaAs/AlAs resonant tunnelling diodes (RTDs) under magnetic field parallel to the tunnel current. We have observed that the polarization degree from the quantum well (QW) and the 2DHG formed at the accumulation layer is highly voltage and light sensitive and exhibits a clear sign inversion. Our results indicate that the voltage dependence of the QW polarization degree is mainly due to an efficient hole-resonant tunnelling process through spin states of the QW. On the other hand, the voltage dependence of the 2DHG polarization degree seems to be dependent on the hole density which is controlled by the applied voltage across the RTDs.
Circular polarization from a nonmagnetic p-i-n resonant tunneling diode
Applied Physics Letters
The authors investigate the circular polarization of the electro- and photoluminescence emissions from the quantum well and contact layers of a nonmagnetic GaAs–AlAs p-i-n resonant tunneling diode under an external magnetic field. The contact emission evidences the formation of a spin polarized two-dimensional electron gas at the n-accumulation layer. The quantum well electroluminescence presents a strong σ− degree of polarization, even for null Zeeman splitting energies, and a slight bias dependence. The observed circular polarization is mainly attributed to the spin polarization of the electrons injected into the quantum well from the two-dimensional electron gas.
Circular polarization in n-type resonant tunneling diodes with Si delta-doping in the quantum well
2014 29th Symposium on Microelectronics Technology and Devices (SBMicro), 2014
In this work, we have investigated magneto-transport and polarization resolved photoluminescence of a GaAs IAIGaAs resonant tunneling diode with Si delta-doping at the center of the quantum well under a magnetic field parallel to the tunnel current. Three resonant peaks were observed in the current-voltage characteristics curve (J(V)) which were associated to donor-assisted resonant tunneling, electron resonant tunneling and to phonon assisted resonant tunneling. The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affect the spin-polarization of carriers in the well. The quantum well photoluminescence shows strong circular polarization degrees with values up to 85% under J 5T at the donor assisted resonant tunneling peak voltage. Our results can be exploited for fitture development of voltage-controlled spintronics devices.
Light controlled spin polarization in asymmetric n-type resonant tunneling diode
Applied Physics Letters, 2007
The authors have observed a strong dependence of the circular polarization degree from the quantum well emission in an asymmetric n-type GaAs/ AlAs/ AlGaAs resonant tunneling diode on both the laser excitation intensity and the applied bias voltage. The sign of the circular polarization can be reversed by increasing the light excitation intensity when the structure is biased with voltages slightly larger than the first electron resonance. The variation of polarization is associated with a large density of photogenerated holes accumulated in the quantum well, which is enhanced due to the asymmetry of the structure.
Physica E: Low-dimensional Systems and Nanostructures, 2000
We present a study of interacting, separately conÿned electron and hole layers that are photoexcited in undoped GaAs=AlAs mixed types I-II quantum wells. The low-temperature interband photoluminescence spectra and circularly polarized integrated intensity were studied as a function of a perpendicularly applied magnetic ÿeld (B67 T) and 2DEG density (n e68 × 10 11 cm −2 ). The observed rich structure of the lowest Landau index magnetoexcitons and the strong intensity oscillations at integral ÿlling factors are interpreted as due to cooperative 2DEG-2DHG transitions and, possibly, to the formation of weakly bound inter-layer excitons. ?
Tunnelling of photogenerated holes through landau levels in GaAs/AlGaAs double barrier diodes
2003
The experimental observation of Landau levels due to the quantization of the transverse moment of holes in resonant tunneling diodes is reported in this work. At very low bias, the photocurrent versus voltage curves, measured under a magnetic field perpendicular to the barrier planes, exhibited several peaks associated to this phenomenon. The analysis of the peak position as a function of the magnetic field reveals several interesting features as non-parabolicity of the valence band, diamagnetic behavior and repulsion between levels with the same Landau-level index.
The results of experimental investigation of the vertical electron transport in a GaAs/Al 0.3 Ga 0.7 As/GaAs single-barrier tunneling heterostructure with a doped barrier are presented. Twodimensional accumulation layers appear on different sides of the barrier as a result of the ionization of Si donors in the barrier layer. The nonmonotonic shift of the current peak is found in the I-V curve of the tunneling diode in a magnetic field perpendicular to the planes of two-dimensional layers. Such a behavior is shown to be successfully explained in the model of appearing the Coulomb pseudogap and the pinning of the spin-split Landau levels at the Fermi levels of the contacts. In this explanation, it is necessary to assume that the Landé factor is independent of the filling factors of the Landau levels and is g * = 7.5 for both layers.