H. Behmenburg

RWTH Aachen University, Aachen, North Rhine-Westphalia, Germany

Are you H. Behmenburg?

Claim your profile

Publications (37)30.16 Total impact

  • Solid-State Electronics 11/2013; · 1.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate the application of nitrogen (N) implantation in GaN as a current-blocking layer. In a first step, vertical current-blocking behavior was confirmed by processing quasi-vertical Schottky diodes with full-area N-implantation. The leakage current was only 10 −6 A cm −2 in forward and reverse directions. Also, the regrowth of AlGaN/GaN heterostructure field-effect transistors on N-implanted and, for reference, non-implanted GaN templates is demonstrated. Even though a decrease in the mobility and sheet carrier density of the two-dimensional electron gas was observed, excellent off-state properties were achieved. Regrown devices exhibited leakage currents as low as 10 −7 mA mm −1 , showing very good quality of the regrowth interface. However, a detailed analysis with pulsed I–V and C–V measurements suggest an increased presence of traps due to regrowth, especially on N-implanted templates.
    Semiconductor Science and Technology 01/2013; 28(8):085006. · 1.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An important issue in multi-step epitaxial growth processes are the electrical characteristics of regrown interfaces. Here, we present a study on interface quality and its effect onto insulating behavior and scattering effects in planar transistors. A double heterostructure with an AlGaN/GaN high electron mobility transistor on top of an AlGaN back-barrier is used to assess electrical properties. Back-barrier templates were exposed to air for several days and subsequently treated by wet and dry chemical etching. A strong impact on leakage behaviour of the regrown interface was observed. Lateral leakage currents as low as 1x10–8 A/mm are achieved with an optimized pre-treatment. Furthermore, under optimized conditions, the regrown GaN channel thickness is varied to investigate the effect of different distances between the two-dimensional electron gas (2DEG) and the regrown interface. Here, enhanced scattering mechanisms, probably due to ionized impurities, lead to a mobility drop of the 2DEG. A parasitic channel is observed, which indicates the presence of additional impurities at the regrown interface. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 01/2013; 10(5):799-802.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier In0.11Al0.72Ga0.17N/GaN heterostructure on sapphire substrate are fabricated and characterized. This structure shows a very high Hall electron mobility of 2200 cm2/V·s, which is the highest value ever reported on In-containing GaN-based HEMTs. For T-shaped gate transistor with a gate length of 75 nm, current gain (ft) and power gain (fmax) cutoff frequencies of 113 and 200 GHz are extracted from S-parameter measurements, respectively. Nonlinear characterization of a T-shaped gate device with a gate length of 225 nm gives an output power density of 2 W/mm at 40 GHz. These results clearly demonstrate the capabilities of such quaternary barrier-based devices.
    IEEE Electron Device Letters 01/2013; 34(8):978-980. · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Enhancement mode GaN-based devices can be realised i.a. by gate recessing or the utilisation of a thin barrier. Yet, as this concept bases upon an increase in barrier capacitance, the application of a gate dielectric causing a capacitance reduction remains as a critical issue. A charge-free dielectric would shift the threshold voltage to negative values, eventually forming a depletion mode device. However, with an appropriate charge-containing dielectric, the same threshold voltage as for an HFET could be maintained. Here, a metal stack consisting of Al and Ti on top of a quaternary In0.11Al0.72Ga0.17N barrier was plasma-oxidised and is shown to form insulated-gate devices with almost the same threshold voltage as their Schottky gate counterparts. The effects on the threshold voltage are discussed. It is shown that the transconductance improves by more than 80%, record drain current of 860 mA/mm is achieved and the dynamic behaviour dramatically improves. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 01/2013; 10(5):840-843.
  • [Show abstract] [Hide abstract]
    ABSTRACT: GaN-based heterostructures are widely used nowadays in many applications such as high brightness light emitting diodes (LEDs), semiconductor lasers, photodetectors, transistors, solar cells, etc. An advantage of AlxInyGa1-x-yN compound over other wide-gap materials is potential ability to cover spectral region from deep ultraviolet (UV) (˜198 nm corresponding to AlN) to infrared (˜1,770 nm corresponding to InN). Creating of effective optoelectronic devices operating in deep UV region and finding of low-cost and practically feasible substrates for GaN heteroepitaxy are the main objectives in GaN-based technology today. In the present work, several examples of fabrication of GaN-based electronic devices are considered, i. e. blue InGaN/GaN LED (˜475 nm) grown on silicon substrate; blue InGaN/GaN LED emitting polarized light (˜450 nm, polarization degree ˜0.42) grown on LiAlO2 substrate; high sensitive metal-semiconductor-metal AlGaN/GaN UV photodetector (η ˜ 4×107 A/W); AlGaN-based UV LED (300-340 nm); optically pumped AlGaN-based UV lasers emitting at 303 and 295 nm with laser threshold of ˜1 MW/cm2.
    01/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on the metal organic vapour phase epitaxy (MOVPE) and characterization of n-type InGaN films for application in direct solar water splitting. The 40 nm thick films exhibit an In fraction of 15% and show good structural quality and a surface root mean square (RMS) roughness of only 0.7 nm. An electron concentration of 9 × 1018 cm-3 at a mobility of 185 cm2/Vs is assessed. The emission peak in photoluminescence (PL) spectra taken at room temperature (RT) is at 2.8 eV, which is consistent to transmission data and the expected bandgap value for this composition. Illumination of the InGaN electrode with a Xe lamp in a 1 M NaOH electrolyte solution at zero external voltage induces a photocurrent (PC) of 0.13 mA/cm2 with a pronounced overshoot in the first few seconds, which we explain by the discharging of a Helmholtz bilayer capacitor. The PC linearly increases with applied voltage while the estimated total conversion efficiency peaks at 0.6 V. Although hydrogen bubbles visibly evolve from the Pt counter electrode, total conversion efficiencies are limited to 0.05%, which is ascribed to incomplete utilization of the optical excitation spectrum and low thickness of both the InGaN film and the space charge region at the semiconductor surface. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 03/2012; 9(3-4):964-967.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A lattice-matched InAlGaN/GaN heterostructure with a barrier-layer thickness of 4 nm has been grown and passivated in situ with a 63-nm SiN by metal–organic chemical vapor deposition. Enhancement-mode heterostructure field-effect transistors have been realized by a fluorine-based surface treatment after the local removal of the SiN. The threshold voltage and transconductance were 0.65 V and 250 mS/mm, respectively, for a 1-$\mu\hbox{m}$ gate-length device. The benefits of an in situ SiN passivation are demonstrated: first, the stabilization of the barrier material and prevention from oxidation and second, the improvement of the device characteristics by reduced source resistance and reduced trapping effects.
    IEEE Electron Device Letters 01/2012; 33(4):519-521. · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: InAlGaN/GaN heterostructure field effect transistors (HFETs) with a nearly lattice-matched barrier layer (thickness tbar = 8.3 nm) are investigated. The focus is set on resolving the systematic dependence of device characteristics on the gate length LG. Therefore, five different gate length devices with LG ranging from 75 nm to 2 µm have been realized. Peak values of 460 mS mm−1 and 100 GHz for transconductance gm and unity current gain cut-off frequency fT are obtained for the 75 nm device. DC characteristics as well as the cut-off frequency fT show systematic scaling with the gate length LG. Nevertheless, short-channel effects appear for the short gate length devices in both DC and RF operation, and a critical minimum aspect ratio LG/tbar of 27 is identified for the investigated barrier composition of xIn = 0.11; yAl = 0.63 and zGa = 0.26.
    Semiconductor Science and Technology 01/2012; 27(3). · 1.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper highlights the electrical characterization of 4 types of the Schottky structures prepared on InAlN/GaN epi-layer designed for HEMT's with the AlN buffer layer and semi-insulating 6H-SiC substrate, which have different mechanical strain due to different growth conditions, using capacitance-voltage and Deep Level Transient Spectroscopy methods (DLTS). The sudden fall of capacitance in the range of reverse voltage from -2.5 to -3.3 V is caused by heterostructure's interface depletion. According to the DLTS measurement it is highly probable that the similar system of defects is present in all samples. Parameters of 7 hole-like traps were identified. Three of them HT1 (1.48 eV) HT2 (1.06 eV) and HT4 (1.01 eV) are certainly present in two structures and one HT3 (1.24 eV) in three structure. The highest concentration of defects has structure with the highest mechanical strain (Strain Raman 2 GPa).
    Advanced Semiconductor Devices & Microsystems (ASDAM), 2012 Ninth International Conference on; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this letter, small- and large-signal measurements of an In<sub>0.15</sub>Al<sub>0.82</sub>N/AlN/GaN high-electron-mobility transistor (HEMT) grown on a sapphire substrate with a 225-nm T-shaped gate are described. A maximum dc current density of 1.2 A/mm and a peak extrinsic transconductance of 460 mS/mm are obtained. The device exhibits a current gain cutoff frequency ( F <sub>T</sub>) and a power gain cutoff frequency ( F <sub>MAX</sub>) of 52 and 120 GHz, respectively. At V <sub>DS</sub> = 15 V, a continuous-wave output power density of 2.9 W/mm was achieved at 18 GHz with an associated power-added efficiency of 28% and a power gain of 15 dB. It is the best value ever reported from InAlN/GaN HEMTs grown on a sapphire substrate.
    IEEE Electron Device Letters 12/2011; · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we report on the thermal oxidation of AlInN/AlN/GaN heterostructures. A “nearly native” Al2O3 oxide was formed during this oxidation procedure, which can be used as a gate oxide and thus enables the fabrication of metal insulator semiconductor hetero field effect transistors. A constant barrier height of ΦB ≈ 2.34 eV was obtained for all oxidized samples, independent of the oxidation time and temperature, indicating a stable AlInN-oxide interface. The interface state density was approximated to be as low as Nint = 2.5 × 1012 cm-2. Oxide thicknesses were estimated to be in the range of 0.6 nm and 3.2 nm, resulting in a suppression of reverse leakage currents oflarge area metal insulator semiconductor diodes by up to three orders of magnitude. Two-dimensional electron gas density and, in particular, carrier mobility are strongly affected by the thermal oxidation in the O2 atmosphere. A narrow processing window for successful thermal oxidation was identified, covering temperatures between 700 °C and 800 °C and durations of few minutes. The resulting oxide thickness scales well with the square root of oxidation time, indicating diffusion of oxygen atoms into the barrier.
    Journal of Applied Physics 10/2011; 110(8):084501-084501-5. · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on a new planetary hotwall research system with independent control of the ceiling and susceptor temperatures. This allows a study of the influence of an actively heated ceiling during a MOCVD process. It was found that the temperature profile across the substrate becomes more uniform when the ceiling temperature is increased while maintaining the same susceptor surface temperature.The parasitic coating on the ceiling was found to be stable and no source of particles up to 1050 °C. The influence of the ceiling temperature on the depletion profile and the possibility to manipulate it was investigated. Good thickness homogeneity of 1.35% (1·σ) on a 4″ sapphire wafer was achieved with excellent XRD results of 206 arcsec for the (0002) reflex and 272 arcsec for the (10-12) reflex for a 4.7 µm thick GaN film. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 07/2011; 8(7‐8).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Our study shows the impact of the process parameters V/III ratio, pressure and temperature on growth and morphology of GaN nanowires (NWs) synthesized by an Au-initiated vapour-liquid-solid mechanism on a sapphire substrate. We confined a temperature window for successful GaN NW growth and show how the variation of reactor pressure changes the NW morphology. Using a very low V/III ratio, NW tapering, which was observed for higher V/III ratios, could be avoided. The optimization of these process parameters led to non-tapered GaN NWs, aligned perpendicular to the substrate. Further evaluation by scanning electron microscopy showed a high density (∼3·109/cm2) of hexagonal c-plane GaN NWs having diameters of 60 ± 9 nm. Transmission electron microscopy revealed single-crystalline NWs without threading dislocations but some stacking faults. The use of a very low V/III ratio was found to be important for the successful selective growth and, most interestingly, led to a difference in NW and gold catalyst droplet diameter. For chemical analysis of the NW and its catalyst droplet, electron energy loss spectroscopy was employed confirming gold as the catalyst material (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 07/2011; 8(7‐8).
  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to optimize the growth conditions, the effect of the most important growth parameters such as growth temperature, pressure and V/III ratio on MOCVD-grown InN was investigated. A series of samples were grown by changing the growth temperature from 500 °C to 550 °C at fixed growth pressure of 800 mbar and V/III ratio of 145000. An improvement of electrical properties with temperature increment was noted. The highest mobility of 1200 cm2/Vs was achieved at 550 °C with a bulk carrier concentration of 4.32 x 1018 cm-3. The effect of V/III ratio on In droplet formation and on carrier concentration was also studied. At fixed temperature of 520 °C, reactor pressure of 200 mbar and at fixed NH3 flow of 3 slm, a rising TMIn flow from 1.2 µmol/min to 2.0 µmol/min results in a carrier concentration increment from 6.06 x 1018 cm-3 to 1.33 x 1019 cm-3and a decrement of the mobility from 430 cm2/Vs to 348 cm2/Vs. X-ray diffraction measurements show that the intensity associated with In droplets on the surface is rising with increasing TMIn flow. The effect of reactor pressure on InN growth was also examined. A high sensitivity to growth pressure for crystalline quality of InN was observed. The full width at half maximum (FWHM) values of InN (0002) reflexes decreased with increasing reactor pressure. With increasing growth pressure above 200 mbar, FWHM of around 275 arcsec of InN (0002) was achieved. This FWHM value is the lowest reported in literature for MOCVD-grown InN so far. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 07/2011; 8(7‐8).
  • [Show abstract] [Hide abstract]
    ABSTRACT: We study the oxygen incorporation during growth of m-plane GaN films on LiAlO2 substrates by metal organic vapour phase epitaxy (MOVPE). A broad peak at ∼550 nm in photoluminescence spectra is probably caused by oxygen impurities. Secondary ion mass spectroscopy (SIMS) confirms this finding and reveals a concentration in the order of 1019 cm-3 which is consistent to the measured n-type doping level. A general slow decrease of the oxygen concentration in growth direction is observed. A c-plane GaN film grown on sapphire co-loaded together with a piece of LiAlO2 shows a slightly increased doping concentration compared to a c-plane GaN reference. However, the achieved concentration of ∼1017 cm-3 is much lower compared to m-plane GaN films. Growth of GaN on a backside-coated GaN/LiAlO2 template does neither suppress the impurity incorporation. This implies that oxygen incorporation via the gas phase is not the dominant factor. The SIMS oxygen profile of this GaN film on the template shows a strong peak at the position of growth interruption indicating the formation of a surface oxide. We assume that the m-plane GaN surface has a large affinity for oxygen at the deposition temperature which leads to the high oxygen impurity level. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 07/2011; 8(7‐8).
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ordinary dielectric function (DF) is presented for high quality Al-rich Al1−xInxN alloy films pseudomorphically grown on GaN in the photon energy range 1–18 eV determined by spectroscopic ellipsometry at room temperature (synchrotron radiation – BESSY II). The (0001)-oriented layers with In content of 14.3 and 15.4% were grown by metal-organic vapour phase epitaxy on thick GaN buffers with sapphire substrates. The sharp onset of the imaginary part of the DF defines the direct absorption edge. In previous studies the DF of Al-rich AlInN were investigated in the photon energy range 1–10 eV, and three high-energy critical points (CPs) of the band structure (Van Hove singularities) were observed. The current study was performed in the extended photon energy range 10–18 eV and three CPs of the band structure at ∼10.6, ∼12.5 and ∼14.2 eV were detected. XRD measurements revealed the pseudomorphic growth of AlInN films and yielded the composition. Finally, the band gap value of 4.68 eV and high-frequency dielectric constant value of 4.55 were evaluated for sample with 15.4% In content.
    Physica Status Solidi (A) Applications and Materials 05/2011; 208(7):1517 - 1519. · 1.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: DC and RF performances of an In0.15Al0.85N/AlN/GaN high electron mobility transistor (HEMT) on sapphire substrate with 8.3 nm barrier layer thickness are reported. The device provides a maximum DC current density of 1 A/mm and a peak extrinsic transconductance of 325 mS/mm. A current gain cutoff frequency (FT) of 80 GHz and a power gain cutoff frequency (FMAX) of 130 GHz are obtained for a 110 nm gate length transistor corresponding to the highest reported values from InAlN/AlN/GaN HEMTs grown on sapphire substrate.
    Electronics Letters 01/2011; · 1.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, the influence of V/III molar flow ratio during AlN growth on SiC on growth mode and in-plane strain is investigated. AlN layers of ∼300nm thickness were grown by metal-organic vapor phase epitaxy (MOVPE) on semi-insulating 6H-SiC and the V/III ratio was changed from 240 to 8200 on four samples by varying the ammonia flux only. The surface morphology was investigated by atomic force microscopy and a growth mode change from two-dimensional to three-dimensional with increasing V/III ratio was observed. Investigation by X-ray diffraction (XRD) reciprocal space mapping (RSM) shows a strong dependence of the AlN peak position on the V/III ratio indicating a significant change in the lattice constants. Results from micro-Raman spectroscopy measurements verify that the AlN in-plane strain can be converted from tensile to compressive when high V/III ratios are applied. Further, an impact of the AlN properties on coalescence time for subsequently grown GaN was found.
    Journal of Crystal Growth 01/2011; 316(1):42-45. · 1.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we report on the thermal oxidation of AlInN/AlN/GaN heterostructures. A ‘nearly-native’ Al2O3 oxide was formed during this procedure, which can be used as a gate oxide and thus enables the fabrication of MIS-HFET. 2DEG density and, in particular, carrier mobility are strongly affected by the thermal treatment in O2 atmosphere. Hence, only a narrow processing window for successful thermal oxidation was identified, covering annealing temperatures between 700 °C and 800 °C and annealing durations of few minutes. Oxide thicknesses estimated to be in the range of 0.6 nm and 2.6 nm were fabricated, enabling a suppression of reverse leakage currents of MIS large-area gate diodes by up to three orders of magnitude. The resulting oxide thickness scales well with the square root of oxidation time, indicating a diffusion of oxygen atoms into the barrier. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 01/2011; 8(7-8):2213-2215.