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We report on effective injection of spin-oriented carriers from a semimagnetic semiconductor structure to a non-magnetic ZnCdSe/ZnSe quantum well (QW). A short-period ZnMnSe/CdSe fractional monolayer superlattice was used as a spin injector. The carriers are photo-generated in the semimagnetic region, spin-polarized via the effect of giant Zeeman splitting and then injected into the non-magnetic QW. The spin injection efficiency was estimated by circular polarization measurements of recombination emission from the QW. The maximal detected degree of the spin polarization is about 25%.In the past few years there has been growing interest in a new concept of electronic devices for data storage and processing -the so-called "spintronics". The basic idea of spintronics is the manipulation by electron spin rather than by electric charge [1]. The design of effective injectors of spin-oriented carriers is necessary for all types of spin devices. A perfect spin injector must operate without application of external magnetic field and at ambient temperature, but despite the significant efforts of numerous research teams this goal has not been achieved so far.Until recently, the most successful realizations of the injection of spin-polarized electrons have employed diluted magnetic semiconductors (DMS) [2][3][4][5]. Both II-VI semimagnetic semiconductors [2-4] and III-V ferromagnetic semiconductors [5] were used to demonstrate injection of spins into either a bulk non-magnetic II-VI layer [2] or a non-magnetic III-V quantum well (QW) structure [3][4][5]. The best achieved values of operation temperature at still reasonable injection efficiency (about 10%) are 6 K for a ferromagnetic p-GaMnAs injector [5] and about 35 K for a BeMnZnSe injector [3]. So the problem of spin injection into semiconductor structures still remains very topical. The further progress in this field is closely connected with fundamental studies of spin transport and relaxation as well as with the search of novel spin injecting materials and structures.In the present paper we propose and study a spin injector based on a II-VI quantum heterostructure -a CdSe/ZnMnSe semimagnetic fractional monolayer (FM) superlattice (SL). For this purpose we have designed a sample including the DMS FM SL with an attached non-magnetic ZnCdSe QW. Previously, similar structures with a non-mag-1 ) Corresponding author;

supporting

confidence: 80%

Semimagnetic ZnMnSe/CdSe Fractional Monolayer Superlattice as an Injector of Spin‐Polarized Carriers

Terent'ev

Торопов

Sorokin

et al. 2002

“…As for the magnetic field range investigated the cyclotron energy hw c is much smaller than the exciton binding energy E B , the diamagnetic shift of the exciton signal is expected to be proportional to B 2 [26]. In the limit of strong confinement Walck and Reinecke gave an expression for the diamagnetic shift DE dia [27] …”

Section: Sample Preparation and Experimentsmentioning

confidence: 99%

Optical Spectroscopy on Non-Magnetic and Semimagnetic Single Quantum Dots in External Fields

Bacher

Schömig

Seufert

et al. 2002

We demonstrate the ability to control the eigenstates in single quantum dots by applying welldefined external fields. Electric fields oriented in-plane as well as perpendicular to the disc-shaped dots allow a modification of the spatial part of the excitonic wavefunction, giving access to the charge distribution in the dot. In contrast, magnetic fields modify the spin part of the wavefunction, resulting in a Zeeman splitting and a diamagnetic shift of the photoluminescence emission. We used the unique property of semimagnetic quantum dots to tailor the effective g-factor, i.e. the sensitivity of the eigenstates to external magnetic fields, by about two orders of magnitude simply by varying the Mn concentration in the dots.Introduction Semiconductor single quantum dots (SQDs) are often designated as 'artificial atoms', because their discrete energy level structure very much resembles that of 'real' atoms. In contrast to atoms, however, the eigenstates in SQDs can be modified by varying the extension or the composition of the quantum dots. For that reason, semiconductor SQDs represent a new class of materials with size dependent electronic, optical or even magnetic properties. This has caused a huge interest in such systems both from a basic physics point of view as well as due to fascinating device concepts like single electron devices, single photon sources or quantum computing. In this context, two topics are of strong interest: (i) the ability to control the occupation of SQDs with a discrete number of electrons and/or holes and (ii) the feasibility to manipulate the SQD eigenstates in a well-defined manner by using external electric or magnetic fields.The most convenient technique to vary the SQD occupation with electron-hole pairs is optical excitation. Simply by changing the excitation power, SQDs can be occupied by either one, two or even more electron-hole pairs and indeed, lots of recent publications have been devoted to optical studies on single excitons, biexcitons or multiexcitons in both, III-V [1-5] and II-VI [6-11] SQDs. In order to achieve a SQD occupation with an unequal number of electrons and holes, one may use above-barrier optical

“…The magnetic field dependences of the ground states are described by the Zeeman effect and a diamagnetic shift [7]. Information about the band structure can be obtained from effective exciton g-values and exciton wavefunctions are measurable through the diamagnetic coefficient.…”

Section: Magneto-reflectivitymentioning

confidence: 99%

“…Figure 1a shows the magneto-reflectivity from the 5 nm quantum well in the region of the LH-1s, HH-1s and HH-2s peaks. The behaviour is typical of all the samples studied in which both the 1s peaks show a well resolved spin splitting above $25 T. Assuming additional band mixing and the exchange interaction to be negligible [8] the ground state transition energies can be described by a sum of zero-field energy, diamagnetic shift and Zeeman splitting [7],…”

Section: Magneto-reflectivitymentioning

confidence: 99%

Excitonic Properties of ZnS Quantum Wells in ZnMgS

Urbaszek

Townsley

Tang

et al. 2002

The excitonic properties of cubic ZnS quantum wells in ZnMgS are studied by reflectivity and magneto-optics. A remarkable improvement in the quality of the samples grown by MBE on GaP substrates has allowed the observation of heavy and light hole exciton transitions with values for the FWHM as narrow as 5 meV. The 2s state of the heavy hole exciton is identified and exciton binding energies as high as 55 meV are deduced, indicating that for quantum wells narrower than 3.5 nm the exciton-LO phonon scattering can be suppressed. Zeeman splittings of the order of 10 meV for both the light and heavy hole exciton transitions appear in magneto-reflectivity spectra in magnetic fields up to 54 T. Large light hole exciton g-values of the order of four for all quantum wells are obtained due to the light hole being the uppermost valence band in these tensile strained quantum wells. A strong reduction in the diamagnetic shifts for narrow wells is observed due to increasing quantum confinement.