Browsing by Author "HARTNAGEL, H. L."

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  • 183 GHz Mixer on InGaAs Schottky Diodes 
    OPREA, I.; WALBER, A.; COJOCARI, O.; GIBSON, H.; ZIMMERMANN, R.; HARTNAGEL, H. L. (Oxford, 2010)
    This work reports on experimental results of a 183 GHz sub-harmonically pumped mixer based on InGaAs antiparallel diode pair. The diode structure provides extremely low parasitic capacitance of about 2.5 fF. Roughly estimated ...
  • Ballistic Charge Carrier Devices for Terahertz 
    HARTNAGEL, H. L. (Technical University of Moldova, 2011)
    It is of great interest, to produce light-weight Terahertz sources for the many appl ications such as security testing. By reducing the transit distance suitably, the charge carrier can be approximately ballistic, that is ...
  • Broadband power detector using a circularly-toothed planar logarithmic-periodic antenna 
    SYDLO, C.; KÖGEL, B.; COJOCARI, O.; FEIGINOV, M.; HARTNAGEL, H. L.; MEISSNER, P. (IEEE, 2005)
    A broadband antenna has been coupled to a planar Schottky diode for the realisation of a sensitive power detector for mm-wave frequencies. The measured response curve is in agreement with calculations and shows values of ...
  • Charge carrier distribution in free-standing porous GaP membranes studied by Raman spectroscopy 
    SARUA, A.; TIGINYANU, I. M.; URSAKI, V. V.; IRMER, G.; MONECKE, J.; HARTNAGEL, H. L. (ELSEVIER, 1999)
    Free-standing porous GaP membranes were fabricated by anodic etching of (111)-oriented crystalline substrates in H2SO4 aqueous solution. The formation of a column-shaped porous structure with average structure dimension ...
  • Correlation between morphology and cathodoluminescence in porous GaP 
    STEVENS-KALCEFF, M. A.; TIGINYANU, I. M.; LANGA, S.; FÖLL, H.; HARTNAGEL, H. L. (American Institute of Physics, 2001)
    Porous layers fabricated by anodic etching of n-GaPn-GaP substrates in a sulfuric acid solution were studied by electron microscopy and cathodoluminescence (CL) microanalysis. The morphology of porous layers was found to ...
  • DC- and IF-noise performance optimization of GaAs Schottky diodes for THz applications 
    COJOCARI, O.; BIBER, S.; MOTTET, B.; RODRIGUEZ-GIRONES, M.; HARTNAGEL, H. L.; SCHMIDT, L.-P. (IOP Publishing, 2004)
  • Design of New Nonlinear Optical Materials Based on Porous III–V Compounds 
    TIGINYANU, I. M.; KRAVETSKY, I. V.; MAROWSKY, G.; MONECKE, J.; HARTNAGEL, H. L. (John Wiley & Sons, Inc, 2000)
    Bulk and porous membranes of gallium phosphide have been characterized by optical second harmonic generation (SHG) technique using a 1064 nm pump beam. The porous membranes prove to exhibit an enhanced SHG in comparison ...
  • Electron field emission from narrow band gap semiconductors InAs 
    LITOVCHENKO, V.; EVTUKH, A.; SEMENENKO, M.; GRYGORIEV, A.; YILMAZOGLU, O.; HARTNAGEL, H. L.; SIRBU, L.; TIGINYANU, I. M.; URSAKI, V. V. (IOP Publishing, 2007)
    We propose to use InAs for the development of effective electron field emitters on the basis of a new technological approach for the preparation of highly textured surfaces which allows one to obtain peculiar fine rod-like ...
  • Enhanced efficiency of p-GaN/n-ZnO light-emitting diodes by using NiO and ZnSe interlayers 
    SIRKELI, V. P.; YILMAZOGLU, O.; KÜPPERS, F.; HARTNAGEL, H. L. (Technical University of Moldova, 2015)
    We report the results from numerical simulations of p-GaN/n-ZnO light-emitting diodes (LEDs) with different architectures. p-GaN/n-ZnO, p-GaN/p-NiO/n-ZnO, and p-GaN/p-NiO/n-ZnSe/n-ZnO LED structures have been examinated ...
  • Experimental validation of thermal model of MM-Wave frequency multipliers 
    OPREA, I.; COJOCARI, O.; SOBORNYTSKYY, M.; HARTNAGEL, H. L. (IEEE, 2013)
    This paper presents a method for estimation of junction temperature of a Schottky diode used in a recently developed frequency doubler to 332 GHz. Our particular interest was the validation of the thermal model of the diode ...
  • Fröhlich modes in porous III-V semiconductors 
    SARUA, A.; MONECKE, J.; IRMER, G.; TIGINYANU, I. M.; GÄRTNER, G.; HARTNAGEL, H. L. (IOP Publishing, 2001)
    Porous GaP, InP and GaAs structures fabricated by MeV ion-implantation-assisted electrochemical etching were investigated by Raman and Fourier transform infrared spectroscopy. Fröhlich modes in the frequency gap between ...
  • GaN Schottky multiplier diodes prepared by electroplating: a study of passivation technology 
    COJOCARI, O.; POPA, V.; URSAKI, V. V.; TIGINYANU, I. M.; HARTNAGEL, H. L.; DAUMILLER, I. (IOP Publishing, 2004)
    This paper presents the results of a Pt/n-GaN Schottky contact technology development based on electrochemical metal deposition. Three different technological approaches are used to fabricate GaN varactor diodes. The effects ...
  • Heterostructure equivalence of step-recovery diodes for ballistic and diffusive electron resonance - a new concept for THz signal generation 
    HARTNAGEL, H. L.; SCHMIDT, L.-P.; NICOLAE, B.; OPREA, I.; SCHONHERR, D.; ONG, D. S.; SCHUR, J.; RUF, M. (IEEE, 2008)
    A heterostructure equivalent to the well-known step recovery diode principle, arranged as a double structure gives a new nonlinear device for highly efficient harmonic THz signal generation. Like in the case of step recovery ...
  • The impact of process optimization on planar THz-Schottky device reliability 
    MOTTET, B.; SYDLO, C.; KOGEL, B.; ROBILLARD DE, Q.; COJOCARI, O.; HARTNAGEL, H. L. (IEEE, 2004)
    The technological complexity as well as space-application quality standards require sophisticated process control and optimization for reliability improvement of planar THz-Schottky devices. Degradation mechanisms are ...
  • Integration of Ge Nanowire Arrays in Glass Micro-Fibers 
    IOISHER, A.; BADINTER, E.; MONAICO, E.; POSTOLACHE, V.; HARTNAGEL, H. L.; LEPORDA, N.; TIGINYANU, I. (Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova, 2011)
    We report on a technological route for the integration of large arrays of Ge nanowires (NWs) in a human-hair-like glass micro-fiber, the length of the micro-fiber reaching one meter. The route comprises (a) the formation ...
  • Internal quantum efficiency enhancement of InGaN/GaN LEDs with Mg-Si pin-doped GaN quantum barrier 
    KÜPPERS, F.; SIRKELI, V. P.; YILMAZOGLU, O.; AL-DAFFAIE, S.; OPREA, I.; ONG, D. S.; HARTNAGEL, H. L. (Institutul de Fizică Aplicată al AŞM, 2018)
    In this work we study numerically the effect of Mg-Si pindoping of GaN quantum barrier within InGaN/GaN multi quantum wells (MQWs) on the internal quantum efficiency (IQE) of LEDs in comparison with LED devices with undoped, ...
  • Micrometer-size GaN Schottky-diodes for mm-wave frequency multipliers 
    COJOCARI, O.; POPA, V.; URSAKI, V. V.; TIGINYANU, I. M.; MUTAMBA, K.; SAGLAM, M.; HARTNAGEL, H. L. (IEEE, 2004)
    Small-size Pt/n-GaN Schottky diodes are fabricated using electrochemical technique for anode metallisation. Effects of surface passivation and thermal annealing on the interface quality are studied using PL-measurements ...
  • Millimeter-wave receiver based on a folded dipole antenna and Schottky diode for maximum power transfer 
    MONTERO-de-PAZ, J.; UGARTE-MUÑOZ, E.; GARCIA-MUÑOZ, L. E .; SEGOVIA-VARGAS, D.; SCHOENHERR, D.; OPREA, I.; AMRHEIN, A.; COJOCARI, O.; HARTNAGEL, H. L. (IEEE, 2012)
    In this article a millimeter-wave (mm-wave) receiver based on a folded dipole antenna, zero bias Schottky diode and silicon (Si) lens is presented. The antenna is designed in such a way that its input impedance is equal ...
  • A new structural approach for uniform sub-micrometer anode metallization of planar THz Schottky components 
    COJOCARI, O.; MOTTET, B.; RODRIGUEZ-GIRONES, M.; BIBER, S.; MARCHAND, L.; SCHMIDT, L.-P.; HARTNAGEL, H. L. (IOP Publishing, 2004)
    This paper presents the evaluation of a Schottky contact technology based on electrochemical metal deposition. The results of a long-term systematic investigation and optimization of the anode formation process to improve ...
  • A novel system for systematic microwave noise and DC characterization of terahertz Schottky diodes 
    BIBER, S.; COJOCARI, O.; REHM, G.; MOTTET, B.; RODRIGUEZ-GIRONES, M.; SCHMIDT, L.-P.; HARTNAGEL, H. L. (IEEE, 2004)
    An automated system is developed to evaluate a large number Schottky diodes for terahertz applications with respect to their dc and noise characteristics using a highly sensitive noise measurement technique for one port ...

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