Yu. L. Ivanov

Photoluminescence and transport in selectively doped p-GaAs/AlGaAs quantum wells: manifestation of the upper Hubbard band

By selective doping (Be) of the well and barrier regions of p-GaAs/AlGaAs structures we have realized the situation where the upper Hubbard band (A+ centers) has been occupied by holes in the equilibrium. We studied temperature behavior of the Hall effect, variable range hopping conductivity and the photoluminescence spectra of the corresponding structures. The experimental data demonstrated that the binding energy of the A+ states significantly increases with respect to 3D case and strongly depends on well width (9nm,15nm). The localization radii of the A+ states are of the order of well widths.

Tunable cyclotron resonance laser based on hot holes in germanium applied to FIR spectroscopy of GaAs/AlGaAs heterostructures

Abstract We have studied the stimulated far infrared (FIR) cyclotron resonance emission from the heavy holes in germanium. The emission spectrum consists of a single line which is linearly tunable by the magnetic field. We have measured the cyclotron resonance absorption of a GaAs/AlGaAs heterostructure using the stimulated cyclotron resonance emission as a light source for the first time. The photoconductive response of the GaAs/AlGaAs heterostructure is studied as a function of the magnetic field. We found that the photoconductive signal depends strongly on the filling factor.

Application of quantum Hall devices for FIR detection

Abstract We propose a novel concept for FIR light detection by means of Hall devices biased at strong currents. The base of the device operation is the effect of photoinduced breakdown of the integer quantum Hall effect (QHE). We demonstrate experimentally that the increase of the bias current from 100 to 300 μA leads to the photoresponse enhancement by over two orders of magnitude. Application of the presented results for designing a tunable high sensitive FIR photodetector is discussed.

Optical spectroscopy of single beryllium acceptors in GaAs/AlGaAs quantum well

We carry out microphotoluminescence measurements of an acceptor-bound exciton (A0X) recombination in the applied magnetic field with a single impurity resolution. In order to describe the obtained spectra we develop a theoretical model taking into account a quantum well (QW) confinement, an electron-hole and hole-hole exchange interaction. By means of fitting the measured data with the model we are able to study the fine structure of individual acceptors inside the QW. The good agreement between our experiments and the model indicates that we observe single acceptors in a pure two-dimensional environment whose states are unstrained in the QW plain.

Effect of coulomb correlations on luminescence and absorption in compensated semiconductors

The spectra of donor–acceptor light absorption and luminescence in lightly doped and lightly compensated semiconductors are calculated. In the photoluminescence calculation, two limiting cases of long and short carrier lifetimes relative to the carrier-energy relaxation time are considered. It is shown that, at long lifetimes, the photoluminescence spectrum is significantly shifted toward longer wavelengths due to the relaxation of minority charge carriers. At intermediate lifetimes, the photoluminescence spectrum consists of two peaks, which is in good agreement with the experimental data.

Intersubband far-infrared emission and magnetotransport of 2D hole gas in a strong in-plane electric field and transverse magnetic fields

Abstract We observe FIR emission and magnetotransport phenomena of modulation doped p- GaAs AlGaAs multi-quantum wells structures of different well width in a streaming regime. This FIR emission originates from radiative transitions between the upper quantum subbands, where hot holes are trapped by the emission of LO-phonons and the ground quantum state. The importance of the light-heavy states mixing with an increase of confinement effect is shown experimentally. The magnetoresistance in a strong in-plane electric field applied along the [110] crystallographic direction is found to be negative, which is explainedDby strong warping of the constant hole energy surfaces in two-dimensional quantum wells.

Optical orientation of spins in GaAs: Mn/AlGaAs quantum wells via impurity-to-band excitation

The paper reports optical orientation experiments performed in the narrow GaAs/AlGaAs quantum wells doped with Mn. We experimentally demonstrate a control over the spin polarization by means of the optical orientation via the impurity-to-band excitation and observe a sign inversion of the luminescence polarization depending on the pump power. The

Hot luminescence increase of higher subband in semiconductor multi-quantum-well structure under a magnetic field

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Population inversion in the set of light hole Landau levels in germanium

factor of a hole localized on the Mn acceptor in the quantum well was also found to be considerably modified from its bulk value due to the quantum confinement effect. This finding shows the importance of the local environment on magnetic properties of the dopants in semiconductor nanostructures.

Tunable cyclotron-resonance laser in germanium.

Abstract We report on the observation of hot luminescence increase from the second electronic subband in undoped GaAs-AlGaAs multi-quantum-wells (MQWs) structure under application of a magnetic field perpendicular to the layers. We consider it to be due to suppression of acoustic phonon emission which has an oscillating character with magnetic field. This novel effect proves the influence of magnetic field on the occupation of a higher subband and provides a new possibility for creation of population inversion between quantum well subbands.