Spin polarized electric currents in semiconductor heterostructures induced by microwave radiation

We report on microwave (mw) radiation induced electric currents in (Cd,Mn)Te/(Cd,Mg)Te and InAs/(In,Ga)As quantum wells subjected to an external in-plane magnetic field. The current generation is attributed to the spin-dependent energy relaxation of electrons heated by mw radiation. The relaxation produces equal and oppositely directed electron flows in the spin-up and spin-down subbands yielding a pure spin current. The Zeeman splitting of the subbands in the magnetic field leads to the conversion of the spin flow into a spin-polarized electric current.Comment: 3 pages, 4 figure

Cyclotron Resonance Assisted Photocurrents in Surface States of a 3D Topological Insulator Based on a Strained High Mobility HgTe Film

We report on the observation of cyclotron resonance induced photocurrents, excited by continuous wave terahertz radiation, in a 3D topological insulator (TI) based on an 80 nm strained HgTe film. The analysis of the photocurrent formation is supported by complimentary measurements of magneto-transport and radiation transmission. We demonstrate that the photocurrent is generated in the topologically protected surface states. Studying the resonance response in a gated sample we examined the behavior of the photocurrent, which enables us to extract the mobility and the cyclotron mass as a function of the Fermi energy. For high gate voltages we also detected cyclotron resonance (CR) of bulk carriers, with a mass about two times larger than that obtained for the surface states. The origin of the CR assisted photocurrent is discussed in terms of asymmetric scattering of TI surface carriers in the momentum space. Furthermore, we show that studying the photocurrent in gated samples provides a sensitive method to probe the effective masses and the mobility of 2D Dirac surface states, when the Fermi level lies in the bulk energy gap or even in the conduction band

Struktur und elektronische Zustaende von Punktdefekten und ihre Wechselwirkung mit Versetzungen in CdTe

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

THE PLASTICITY OF A SEMICONDUCTING COMPOUND : CdTe, ELECTRICAL MEASUREMENT AND CHEMOMECHANICAL EFFECT

Des cristaux de CdTe ont été obtenus au laboratoire de cristallogénèse de Göttingen (Kristall-Labor), et caractérisés par des mesures d'effet Hall et thermoélectriques. Les dislocations ont été révélées par piqûres d'attaque avant et après indentation réalisée dans différents électrolytes polarisés par rapport à l'échantillon. L'analyse de l'activation thermique semble indiquer qu'un mécanisme de Peierls gouverne la contrainte d'écoulement à la température ambiante et à plus basse température. Aux dislocations introduites par compression est associé un niveau neutre situé à 0,3 eV au-dessus de la bande de valence (selon les mesures d'effet Hall et thermoélectrique). Dans ce matériau la mobilité des dislocations est plus petite dans les conditions de bande plate qu'avec une charge induite sur les défauts dans la couche superficielle du matériau.CdTe has been grown in the Göttingen Kristall-Labor and characterized by Hall effect and thermoelectrical measurements. Dislocations are etch pitted before and after deformation by an hardness indenter. The experiment is performed in various electrolytes while a voltage is applied with respect to the specimen. Thermal activation analysis seems to indicate that a Peierls mechanism determines the flow stress at and below room temperature. The dislocations introduced by compression of p-CdTe give rise to states which are neutral at 0.3 eV above Ev in the Hall effect and thermoelectrical power. Dislocation mobility in this material is smaller under flat band conditions than with an induced charge at defects in the surface layer of this material

Exchange interaction of electrons with Mn in hybrid AlSb/InAs/ZnMnTe structures

Diluted magnetic semiconductor heterovalent AlSb/InAs/ZnMnTe quantum well (QW) structures with an electron channel have been designed and grown applying molecular-beam epitaxy. The enhanced magnetic properties of QWs as a result of the exchange interaction with Mn2+ ions, are proved by measuring the microwave radiation induced spin polarized electric currents