Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 17: Poster I

HL 17.10: Poster

Monday, February 25, 2008, 16:30–19:00, Poster D

THz detectors on the basis of HgTe-Quantum wells — •Fathi Gouider¹, Hartmut Buhman², Christoph Brüne², Günter Hein³, and Georg Nachtwei¹ — ¹Institut of Applied Physics, Technical University of Braunschweig, Mendelssohnstr.2, D- 38106 Braunschweig — ²Universität Würzburg EP III, Am Hubland, D-97074 Würzburg — ³Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig,Germany

The investigations of the THz-photoresponse (PR) of devices with HgTe QWs embedded in CdHgTe barriers are aimed at obtaining photosignals at smaller magnetic fields. The QWs have a thicknes of d_QW =12nm, so that the material HgTe of the QW possesses a semimetallic band structure. We found an effective mass of about m_c = 0.026m₀ for our samples from cyclotron resonance measurements (transmission of THz waves, Voigt configuration, Ge detector). As this cyclotron mass is by about a factor 3 smaller than the one of electrons in GaAs, the same Landau level splitting as in GaAs is reached at about 1/3 of the magnetic field. In this presentation, we present measurements of the THz photoconductivity on quantum Hall systems. HgTe/HgCdTe (MCT) heterostructures with Corbino geometry are investigated. A recipe for the preparation of metallic Corbino contacts on MCT is shown. The system is excited by the radiation of a p-Ge laser (from1.7 to 2.5 THz) and the PR is measured versus the magnetic field B . Because of the lower effective mass in MCT, the cyclotron resonance(CR) in this system appears at a relatively low magnetic field B≈ 2 T.