L. Dobrzanski

Institute of Electronic Materials Technology, Warszawa, Masovian Voivodeship, Poland

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Publications (21)6.44 Total impact

  • A. Jagoda · B. Stańczyk · L. Dobrzański · R. Diduszko
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    ABSTRACT: Radio frequency reactive sputtering was used to produce gallium nitride films on thermally oxidized silicon substrates at room temperature. Metallic Ga (purity 6N) was used as the target, N2 and Ar were utilized as sputtering gases. Amorphous GaN was obtained by metal-induced crystallization with a Ni assistance. The nickel particles were scattered onto the surface by rf sputtering and their density was 2 × 1014 atoms/cm2 or 4 × 1014 atoms/cm2, which corresponds to 0.02 nm and 0.04 nm thick layer. These values are less than a monolayer thickness, so they are not continuous. Samples were annealed at 700 °C for 3 h and at 900 °C for 5 min in a RTP furnace. The 2.5 μm GaN layers grown on the Ni-coated SiO2 surface recrystalized during annealing forming crystals of (002) orientation. The catalytic regrowth mechanism of GaN is discussed on the basis of experimental results. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    No preview · Article · Apr 2007 · physica status solidi (c)
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    ABSTRACT: In this paper, high power LDs based on GaAsP/(AlGa)As heterostructures designed toward reduction of the vertical (perpendicular to junction plane) light beam divergence, intended for λ=810 nm are presented. Insertion of thin, wide-gap barrier layers at the interfaces between the waveguide and cladding layers of original SQW SCH enables separate control of the carrier and optical confinements. According to theoretical modelling, the antiguiding influence of the barriers on the waveguiding properties of the original SQW SCH causes a weakening of the optical confinement and enlargement of a light spot on the laser facet. As a consequence both the emitted light vertical beam divergence reduction and the catastrophic optical damage (COD) level increase can be achieved in the DBSCH LDs.
    No preview · Conference Paper · Jul 2005
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    ABSTRACT: Thermal properties of 808 nm emitting high-power diode lasers are investigated by means of micro-thermography. A thermo-camera equipped with a 384x288 pixel HgCdTe-detector (cut off wavelength at 5.5 micron) and IR-micro-objective is used, which allows for thermal imaging with a spatial resolution of 5 mum. A novel methodological approach for data re-calibration for absolute temperature measurements is proposed. We present steady-state thermal distributions from broad-area devices. The remarkable agreement of this data with the results of modeling work has been reached. Cross-calibration of the micro-thermographic results is obtained by complementary micro-Raman data that give information about facet temperatures with a spatial resolution of about 1 micron. Transient thermal properties are monitored with a temporal resolution of 1.4 ms. Such thermal transients illustrate the heat flow trough the device after turning on the operation current. Special experiments are done in order to detect and localize hot spots at the facet and within the devices. Moreover, we show that the analysis of thermal images can be used as a recognition method of defects hidden inside the cavity, even if they are not detectable by visual inspection. These activities are paving the way towards a novel screening methodology.
    No preview · Article · Mar 2005 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: This paper presents method for facets passivation of high power lasers GaAl As using thin films of AIN and GaN formed by reactive sputtering at low temperature. GaN has been chosen due to its exceptional stability at high temperatures and resistance against attack. GaN is insoluble in acids. Layers of GaN protect AIN coating against influence of chemical and physical factors. We report some problems concerning technology of GaN thin films deposition using RF Sputtering from Ga target in Ar-N2 gas mixtures. Observation of N+ peaks in plasma spectrum provides information on optimal conditions for synthesis of GaN. The quality of GaN layers was examined by X-ray Diffraction (XRD), SIMS method, optical absorption, measurement of refractive index and density. Lasers diodes with coated mirrors of AIN-GaN exhibit good stability during CW life-test.
    No preview · Article · Jul 2003 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: This paper presents results of the investigated levels of Catastrophic Optical Damage of the SQW-SCH lasers mirrors coated with AlN (lambda/4n) layer. These results have been compared with COD levels of this same type of the lasers with mirros coated by Si3N4 (lambda/4n), thick AlN (3lambda/4n) layers, and without coatings.
    Full-text · Article · Jan 2003 · Proceedings of SPIE - The International Society for Optical Engineering

  • No preview · Article · Jan 2003
  • Beata Stanczyk · Andrzej Jagoda · Lech Dobrzanski
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    ABSTRACT: A method of selective gallium nitride (GaN) layer deposition on silicon substrates was developed. The method was developed using mixed plasma and wet etching of GaN and AIN layers and the layers were obtained using reactive sputtering. The quality of layers were examined using secondary ion spectroscopy (SIMS), roentgen diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Rutherford back scattering (RBS). The method was used for the production of semiconductor lasers and quantum dots.
    No preview · Article · Jan 2003 · Proceedings of SPIE - The International Society for Optical Engineering
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    L Dobrzanski · A Jagoda · K Gora · K Przyborowska
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    ABSTRACT: We report on development of MSM and Schottky barrier visible blind detectors on gallium nitride which exhibit responsivities of 0.5 A/W and 0.1 A/W respectively. GaN band edge absorption occurs at 365 nm and naturally provides "visible blindness" of devices. The fabricated Schottky barrier devices exhibit flat spectral response for the UV light. Typical dark current of de-tector is 1 nA per square millimetre. The estimated detectivity and noise equivalent power of our devices are close to the best reported elsewhere.
    Full-text · Article · Dec 2002 · Opto-Electronics Review
  • L. Dobrzanski · A. Kowalik · K. Gora · J. Piotrowski
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    ABSTRACT: The refractive binary aplanatic lenses with dimensions of the wavelength scale have been fabricated and characterized by optical measurements. We fabricated lenses with f/D ratio close to one where f is the effective focal length and D is the lens diameter. Light intensity was measured on the focal surface of lenses using three independent methods and it has been demonstrated that IR light energy was concentrated within an area of diameter probably smaller than 20 μm. Operation of such lens cannot be explained on the basis of ray optics or simulated using scalar diffraction theory which provided contradictory results.
    No preview · Conference Paper · Feb 2002
  • K. Kosiel · L. Dobrzanski · B. Majkusiak · A. Jasik
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    ABSTRACT: The RT (Resonant Tunnelling) AlAs/In0.53Ga0.47 As/InP heterostructure employed in our measurements was deposited on nominally (001) oriented InP:S n+ (2×1018 cm-3 ) substrates. Undoped LP MOVPE layers typically have an unintentional n-type doping level of about 2×1014 cm -3. The material was made by epitaxial growth using LP MOVPE (Low Pressure Metalorganic Vapour Phase Epitaxy) technology and realised in AIX-200 (Aixtron) equipment. The growth temperature controlled by thermo-couple was 653°C for indium containing layers and 750°C for the AlAs lattice mismatched layer. Reactor pressure was 100 mbar. Trimethylcompounds (TMGa, TMAl and TMIn) were group III chemical precursors, while as a source of As and P arsine and phosphine were used, respectively. X-ray diffractometry measurements made for thick test samples confirmed accurate In0.53Ga0.47As (lattice matched to InP substrate) layer composition. Hall method measurements allowed us to determine the doping levels in deposited layers. AFM (Atomic Force Microscopy) measurements (Tapping Mode with scanning frequency lower than 1 Hz) performed for specially grown test structures were applied to confirm interfacial smoothness in AlAs/In0.53Ga0.47As active region. This lack of roughness plays a crucial role in RT physics. Static I-V RTD characteristics obtained in room temperature for a set of mesas show high PVR (Peak to Valley Current Density Ratio) parameters
    No preview · Article · Jul 2001 · Journal of Wide Bandgap Materials
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    ABSTRACT: Strained layer InGaAs/GaAs SCH SQW (separate confinement heterostructure single quantum well) lasers were grown by a molecular beam epitaxy (MBE). Highly reliable CW (continuous wave) 980-nm, broad contact, pump lasers were fabricated in stripe geometry using Schottky isolation and ridge waveguide construction. Threshold current densities of the order of Jth ≈ 280 A/cm2 (for the resonator length L = 700 μm) and differential efficiency η = 0.40 W/A (41%) from one mirror were obtained. The record wall-plug efficiency for AR/HR coated devices was equal to 54%. Theoretical estimations of above parameters, obtained by numerical modelling of devices were Jth = 270 A/cm2 and η = 0.47 W/A from one mirror, respectively. Degradation studies revealed that uncoated and AR/HR coated devices did not show any appreciable degradation after 3000 hr of CW operation at 35°C heat sink temperature at the constant optical power (50 mW) conditions.
    Full-text · Article · Mar 2001 · Opto-Electronics Review
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    ABSTRACT: Presents experimental results obtained with resonant-tunneling diodes fabricated from (GaAl)As/GaAs and (CdMg)Te/CdTe semiconductor heterostructures grown - respectively - by low-pressure metal-organic vapor-phase epitaxy and molecular-beam epitaxy methods. These results demonstrate, firstly, the appearance of intriguing oscillatory structure on the rising slope of the resonant peak in small-diameter (GaAl)As/GaAs-based devices and, secondly, the improvement of current-voltage characteristics of (CdMg)Te/CdTe-based resonant-tunneling diodes due to reduction of their cross-sectional area
    No preview · Conference Paper · Feb 2001
  • Andrzej Jagoda · Lech Dobrzanski · M. Mozdzonek · Sylwia Wrobel
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    ABSTRACT: The authors propose AlN dielectric layer as a mirror coating for AlGaAs SQW-SCH laser diodes. As a semitransparent (low reflective - LR) coating they use a single AlN layer, and as a high reflective coating (HR) they use six pairs of AlN-Si layers. The measured reflection coefficients for LR and HR coatings and optical output power characteristics for coated and uncoated mirrors are presented. The optical output power of diodes with coated mirrors is two times higher than the optical power of uncoated diodes
    No preview · Conference Paper · Feb 2001
  • K. Kosiel · L. Dobrzanski · B. Majkusiak · A. Jasik
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    ABSTRACT: The RT (Resonant Tunnelling) AlAs/In<sub>0.53</sub>Ga<sub>0.47 </sub>As/InP heterostructure employed in our measurements was deposited on nominally (001) oriented InP:S n+ (2×10<sup>18</sup> cm<sup>-3 </sup>) substrates. Undoped LP MOVPE layers typically have an unintentional n-type doping level of about 2×10<sup>14</sup> cm <sup>-3.</sup> The material was made by epitaxial growth using LP MOVPE (Low Pressure Metalorganic Vapour Phase Epitaxy) technology and realised in AIX-200 (Aixtron) equipment. The growth temperature controlled by thermo-couple was 653°C for indium containing layers and 750°C for the AlAs lattice mismatched layer. Reactor pressure was 100 mbar. Trimethylcompounds (TMGa, TMAl and TMIn) were group III chemical precursors, while as a source of As and P arsine and phosphine were used, respectively. X-ray diffractometry measurements made for thick test samples confirmed accurate In<sub>0.53</sub>Ga<sub>0.47</sub>As (lattice matched to InP substrate) layer composition. Hall method measurements allowed us to determine the doping levels in deposited layers. AFM (Atomic Force Microscopy) measurements (Tapping Mode with scanning frequency lower than 1 Hz) performed for specially grown test structures were applied to confirm interfacial smoothness in AlAs/In<sub>0.53</sub>Ga<sub>0.47</sub>As active region. This lack of roughness plays a crucial role in RT physics. Static I-V RTD characteristics obtained in room temperature for a set of mesas show high PVR (Peak to Valley Current Density Ratio) parameters
    No preview · Conference Paper · Feb 2001
  • Andrzej Jagoda · Lech Dobrzanski · Beata Stanczyk
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    ABSTRACT: Summary form only given. The authors report on the technology of GaN synthesis which is based on reactive ion sputtering from a Ga target in a nitrogen atmosphere. This process is carried out at room temperature and in low pressure conditions
    No preview · Conference Paper · Feb 2001
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    ABSTRACT: The photovaractors for microwave photonic application were studied. The photovaractors were fabricated as a planar p-i-n or metal-semiconductor-metal (MSM) photodiodes placed in a pigtailed fiber optical module. The study of S11 parameters in the frequency range up to 3 GHz under illumination has shown that capacitances of p-i-n and MSM photodiodes strongly depend on the optical power. The capacitance variation of the photo-varactor diode under illumination is discussed.
    No preview · Conference Paper · Nov 2000
  • L. Dobrzanski · J.K. Piotrowski · S.A. Malyshev
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    ABSTRACT: Metal-semiconductor-metal photodetectors (MSM PD) based on the InGaAs light-absorbing layer have been fabricated and characterized. It has been demonstrated that despite the non-optimized design, the devices operate well up to 3 Ghz and can compete with professional p-i-n diodes. The conclusions for future device improvement have been drawn
    No preview · Conference Paper · Feb 2000
  • L. Dobrzanski · J. Piotrowski
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    ABSTRACT: A micromachined silicon thermopile and thermal emitters of infrared radiation have been developed. The thermopile junction materials were highly doped polycrystalline silicon deposited by PECVD or RF sputtering and aluminum metallisation. The hot junctions have been placed on a 0.5 μm thick membrane made of silicon nitride, and the cold junctions have been placed on a surface of monolithic silicon. Porous silicon has been used as a thick sacrificial layer to suspend the membrane over the cavity. Alternatively, nanoporous silicon has been exploited as the thermal insulation material. Similar methods have been used for fabrication of electrically modulated microemitters of infrared radiation. This technology enables cost-effective manufacturing of infrared thermal sensors, and high performance emitters
    No preview · Article · Nov 1998 · IEE Proceedings - Optoelectronics
  • L. Dobrzanski
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    ABSTRACT: The physical background of novel small-scale fast semiconductor devices has been presented. The performance constrains of hot electron and quantum devices have been discussed. The prospects of development and application of these devices has been indicated. Experimental structures studied at the Institute of Electronic Materials Technology and technologies needed for their realisation have also been presented
    No preview · Conference Paper · Jun 1998
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    ABSTRACT: This paper presents the development of micromachined thin-film silicon microbolometers which can be used for detection of soft X-ray, UV, visible and infrared radiation. The detector structure is a 1 μm thick polysilicon/Si3N4 membrane suspended over a cavity. This structure has been obtained by anisotropic etching of silicon with a previously deposited polysilicon/Si3N4 sandwich. Alternatively, porous silicon has been used as the sacrificial layer. Devices have been characterized. Good values of the voltage responsivity and detectivity have been obtained.
    No preview · Article · May 1997 · Sensors and Actuators A Physical

Publication Stats

50 Citations
6.44 Total Impact Points

Institutions

  • 1997-2007
    • Institute of Electronic Materials Technology
      Warszawa, Masovian Voivodeship, Poland
  • 1998-2002
    • Institute of Electron Technology
      Warszawa, Masovian Voivodeship, Poland
  • 2001
    • Polish Academy of Sciences
      • Institute of Physics
      Warszawa, Masovian Voivodeship, Poland