G. Trankle

Publications (86)107.95 Total impact

• Article: AlGaN/GaN/GaN:C Back-Barrier HFETs With Breakdown Voltage of Over 1 kV and Low

  E. Bahat-Treidel, F. Brunner, O. Hilt, E. Cho, J. Wurfl, G. Trankle
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  ABSTRACT: A systematic study of GaN-based heterostructure field-effect transistors with an insulating carbon-doped GaN back barrier for high-voltage operation is presented. The impact of variations of carbon doping concentration, GaN channel thickness, and substrates is evaluated. Tradeoff considerations in on-state resistance versus current collapse are addressed. Suppression of the off-state subthreshold drain-leakage currents enables a breakdown voltage enhancement of over 1000 V with a low on-state resistance. Devices with a 5-μm gate-drain separation on semi-insulating SiC and a 7-μm gate-drain separation on n-SiC exhibit 938 V and 0.39 mΩ·cm² and 942 V and 0.39 m Ω·cmcm², respectively. A power device figure of merit of ~ 2.3 × 10⁹ V²/Ω·cm² was calculated for these devices.
  IEEE Transactions on Electron Devices 12/2010; · 2.32 Impact Factor
• Article: Root-Cause Analysis of Peak Power Saturation in Pulse-Pumped 1100 nm Broad Area Single Emitter Diode Lasers

  Xiaozhuo Wang, P. Crump, H. Wenzel, A. Liero, T. Hoffmann, A. Pietrzak, C.M. Schultz, A. Klehr, A. Ginolas, S. Einfeldt, F. Bugge, G. Erbert, G. Trankle
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  ABSTRACT: Many physical effects can potentially limit the peak achievable output power of single emitter broad area diode lasers under high current, pulse-pumped operation conditions. Although previous studies have shown reliable operation to high pump levels (240 A, 300 ns, and 1 kHz), power was found to saturate. We present here results of a systematic study to unambiguously determine the sources of this power saturation. A combination of detailed measurements and finite element device simulation were used for the diagnosis. We find that the measured power saturation is dominated by electron leakage caused by band bending at high bias due to the low mobility of the p-type waveguide. However, the power saturation is only fully reproduced when longitudinal spatial hole-burning is included. Higher powers are expected to be achieved if higher energy barriers and lower confinement factors are used to mitigate leakage and longitudinal hole-burning, respectively.
  IEEE Journal of Quantum Electronics 06/2010; · 1.88 Impact Factor
• Article: 11W broad area 976 nm DFB lasers with 58% power conversion efficiency

  C.M. Schultz, P. Crump, H. Wenzel, O. Brox, A. Maassdorf, G. Erbert, G. Trankle
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  ABSTRACT: A report is presented on how distributed feedback (DFB) lasers can achieve high optical power and power conversion efficiency together with a narrow vertical emission angle. Recently developed 976 nm DFB lasers emit 11 W, have a maximum power conversion efficiency of 58 , a spectral linewidth of 0.4 nm FWHM and a narrow vertical far field of 28 FWHM. This considerable enhancement was obtained with an improved epitaxy design and optimised grating fabrication process. These are DFB lasers that achieve power, efficiency and emission angle values comparable to conventional Fabry-Pe rot lasers, but with spectral stabilisation. Accordingly, these lasers are particularly well suited for pumping fibre and solid-state lasers.
  Electronics Letters 05/2010; · 0.96 Impact Factor
• Article: AlGaN/GaN HEMT With Integrated Recessed Schottky-Drain Protection Diode

  E. Bahat-Treidel, R. Lossy, J. Wurfl, G. Trankle
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  ABSTRACT: We present an AlGaN/GaN high-electron mobility transistor (HEMT) with an integrated recessed protection diode on the drain side of the transistor channel. Results from our Schottky-drain HEMT demonstrate an excellent reverse blocking with minor tradeoff in the on-state resistance for the complete device. The excellent quality of the forward diode characteristics indicates high robustness of the recess process. The reverse blocking capability of the diode is better than - 110 V. Physical-based device simulations give an insight in the respective electronic mechanisms. This is the first time that a recessed Schottky-drain diode integrated in a HEMT device is presented.
  IEEE Electron Device Letters 10/2009; · 2.85 Impact Factor
• Conference Proceeding: Highly robust X-band LNA with extremely short recovery time

  M. Rudolph, M. Dewitz, A. Liero, I. Khalil, N. Chaturvedi, C. Wipf, R.M. Bertenburg, J. Miller, J. Wurfl, W. Heinrich, G. Trankle
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  ABSTRACT: GaN-based low-noise amplifiers (LNAs) recently were shown to provide high ruggedness together with low noise figure. These LNAs allow for simplified receiver architectures, e.g., since no limiter is required to protect the input. This paper for the first time presents an investigation of the recovery time of a highly rugged GaN LNA. The X-band LNA is shown to survive input overdrive powers up to 46 dBm under pulsed and 40 dB under cw conditions, with a noise figure of 2.8 dB. Extremely short recovery times below 10 ns were simulated and proved to be below the measurement resolution.
  Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International; 07/2009
• Article: High-Brightness Quantum Well Tapered Lasers

  B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, G. Trankle
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  ABSTRACT: High-power quantum well lasers with high brightness in the spectral range between 650 nm and 1080 nm will be presented. Improved layer structures with a narrow vertical far-field divergence down to angles of 15deg (full-width at half-maximum) were developed. For these layer structures, optimized tapered lasers were processed to achieve laterally a nearly diffraction-limited beam quality with beam propagation factors smaller than 2. Depending on the emission wavelength, the tapered devices reach an output power up to 12 W and a brightness of 1 GWmiddotcm^-2middotsr^-1.
  IEEE Journal of Selected Topics in Quantum Electronics 07/2009; · 3.78 Impact Factor
• Article: High-Brightness and Ultranarrow-Beam 850-nm GaAs/AlGaAs Photonic Band Crystal Lasers and Single-Mode Arrays

  T. Kettler, K. Posilovic, L.Ya. Karachinsky, P. Ressel, A. Ginolas, J. Fricke, U.W. Pohl, V.A. Shchukin, N.N. Ledentsov, D. Bimberg, J. Jonsson, M. Weyers, G. Erbert, G. Trankle
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  ABSTRACT: Lasers with a waveguide based on a longitudinal photonic band crystal designed for 850 nm emission are investigated. They demonstrate ultranarrow vertical beam divergence of about 7deg full-width at half maximum without using corrective optics. A high internal efficiency of 93% is achieved. Broad-area 50-mum-wide stripe lasers with unpassivated facets show a high total output power of about 20 W in pulsed mode with far-field divergences of 9.5deg and 11.3deg of the slow and fast axis, respectively, equivalent to an ultrahigh brightness of 3×10⁸ Wmiddotcm^-2 middotsr^-1 and a low aspect ratio of only 1.2. Narrow ridge lasers with 5 mum stripes demonstrate more than 1.5 W maximum output power in continuous-wave operation. Large arrays with up to 256 uncoupled single-mode laser diodes demonstrate low threshold currents of about 70 mA per laser, independent of the number of lasers in the array.
  IEEE Journal of Selected Topics in Quantum Electronics 07/2009; · 3.78 Impact Factor
• Conference Proceeding: Influence of GaN cap on robustness of AlGaN/GaN HEMTs

  P. Ivo, A. Glowacki, R. Pazirandeh, E. Bahat-Treidel, R. Lossy, J. Wurfl, C. Boit, G. Trankle
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  ABSTRACT: DC-Step-Stress-Tests of GaN HEMTs have been performed on wafers with and without GaN-cap. The tests consist of a step ramping of drain-source voltage V_DS by 5 V every two hours at off-state. The irreversible evolution of leakage current starting at a certain drain voltage has been taken as a criterion for the onset of device degradation. It has been stated that there is a stability limit for V_DS depending on the epitaxial design. It has been found that wafers with GaN cap show much higher critical voltages as compared to non-capped epitaxial designs. Electroluminescence measurements have been performed to localize defects after DC-Step-Stress-Tests up to 80 V for wafer without GaN cap and 120 V for wafer with GaN cap.
  Reliability Physics Symposium, 2009 IEEE International; 05/2009
• Article: Highly Rugged 30 GHz GaN Low-Noise Amplifiers

  M. Rudolph, N. Chaturvedi, K. Hirche, J. Wurfl, W. Heinrich, G. Trankle
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  ABSTRACT: GaN low-noise amplifiers (LNAs) operating at 27-31 GHz are presented in this letter. The monolithically integrated LNAs were fabricated using the process line of the Ferdinand-Braun-Institut. Noise figures of 3.7 to 3.9 dB were measured. The ruggedness of the LNAs was verified by noise measurements after stressing the LNA for up to 2 h with up to 33 dBm of input power. These conditions are among the most severe stress tests reported in literature. To the best of the authors knowledge, this is the first demonstration of a GaN LNA in this frequency region.
  IEEE Microwave and Wireless Components Letters 05/2009; · 1.72 Impact Factor
• Article: Twin-Contact 645-nm Tapered Laser With 500-mW Output Power

  P. Adamiec, B. Sumpf, D. Feise, K.-H. Hasler, P. Ressel, H. Wenzel, M. Zorn, M. Weyers, G. Erbert, G. Trankle
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  ABSTRACT: High brightness tapered lasers emitting around 650 nm were developed. We realized 2-mm-long devices with 750-mum straight section, 1250-mum tapered section, and 4deg taper angle. The input currents into both sections were independently controlled. The laser reached 500-mW output power in continuous-wave operation in a nearly diffraction-limited beam quality. A modulation efficiency of 7.5 W/A was achieved.
  IEEE Photonics Technology Letters 03/2009; · 2.19 Impact Factor
• Article: Multiple vertical mode high power 975 nm diode lasers restricted to single vertical mode operation through use of optical facet coatings

  P. Crump, H. Wenzel, P. Ressel, G. Erbert, G. Trankle
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  ABSTRACT: A new design approach has been developed for facet coating of high power diode lasers, that is shown to preferentially suppress higher-order guided optical modes, without any degradation in device performance. Repeated optical coating of reference lasers is found to controllably transform the vertical far field from a three-peaked higher-order mode to a single-peaked fundamental mode, in good agreement with simulations. 975 nm devices with such coatings reach power conversion efficiency of 65%.
  Electronics Letters 02/2009; · 0.96 Impact Factor
• Conference Proceeding: Compact Watt-class visible light sources using direct frequency-doubled edge-emitting diode lasers

  K. Paschke, G. Blume, Chr. Fiebig, A. Sahm, D. Feise, M. Uebernickel, G. Ebert, G. Trankle
  Proc. SPIEProc. SPIE, San Jose, CA, USA; 01/2009
• Article: Punchthrough-Voltage Enhancement of AlGaN/GaN HEMTs Using AlGaN Double-Heterojunction Confinement

  E. Bahat-Treidel, O. Hilt, F. Brunner, J. Wurfl, G. Trankle
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  ABSTRACT: In this paper, we present an enhancement of punchthrough voltage in AlGaN/GaN high-electron-mobility-transistor devices by increasing the electron confinement in the transistor channel using an AlGaN buffer-layer structure. An optimized electron confinement results in a scaling of punchthrough voltage with device geometry and a significantly reduced subthreshold drain leakage current. These beneficial properties are pronounced even further if gate-recess technology is applied for device fabrication. Physical-based device simulations give insight in the respective electronic mechanisms.
  IEEE Transactions on Electron Devices 01/2009; · 2.32 Impact Factor
• Article: Wavelength-Stabilized Compact Diode Laser System on a Microoptical Bench With 1.5-W Optical Output Power at 671 nm

  M. Maiwald, A. Ginolas, A. Muller, A. Sahm, B. Sumpf, G. Erbert, G. Trankle
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  ABSTRACT: A wavelength-stabilized compact diode laser system emitting at 671 nm mounted on a microoptical bench with the dimensions of 13 mmtimes4 mm is presented. A reflecting Bragg grating was aligned on the rear side of a broad-area gain medium for wavelength stabilization at 671 nm. A maximum output power of 1.5 W was obtained together with a spectral width of 40 pm (full-width at half-maximum). At 1.0 W, a center wavelength stability below 20 pm over 5 h was determined. With these features, the devices are well-suited for spectroscopic applications.
  IEEE Photonics Technology Letters 11/2008; · 2.19 Impact Factor
• Article: 5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality

  K.-H. Hasler, B. Sumpf, P. Adamiec, F. Bugge, J. Fricke, P. Ressel, H. Wenzel, G. Erbert, G. Trankle
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  ABSTRACT: Distributed Bragg reflector tapered lasers emitting at a wavelength of about 1060 nm were realized. The expitaxial layer structure leads to a vertical far-field angle of 15^deg (full-width at half-maximum). The devices with a total length of 4 mm consist of 2-mm-long ridge waveguide and tapered sections. The input currents to both sections can be independently controlled. The laser reached 5-W output power with a narrow spectral linewidth below 40 pm (95% power) and a nearly diffraction-limited beam quality.
  IEEE Photonics Technology Letters 11/2008; · 2.19 Impact Factor
• Article: Passively Cooled TM Polarized 808-nm Laser Bars With 70% Power Conversion at 80-W and 55-W Peak Power per 100- m Stripe Width

  P. Crump, H. Wenzel, G. Erbert, P. Ressel, M. Zorn, F. Bugge, S. Einfeldt, R. Staske, U. Zeimer, A. Pietrzak, G. Trankle
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  ABSTRACT: Many solid state laser systems rely on transverse- magnetic polarized 808-nm diode lasers, whose efficiency is limited by the transparency current of the quantum well and whose peak power is limited by facet failure. Using optimized epitaxial growth, low voltage designs, and optimized facet reflectivity, we demonstrate 70% power conversion efficiency at 80 W in 1-cm laser bars under continuous-wave (CW) test conditions. We assess peak power limits in single emitters and find that 100-mum stripe lasers roll thermally under the CW condition at 13 W without failure, then reach >50 W under 300-ns pulse condition, where they fail at internal defects.
  IEEE Photonics Technology Letters 09/2008; · 2.19 Impact Factor
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: Switch-mode amplifier ICs with over 90% efficiency for Class-S PAs using GaAs-HBTs and GaN-HEMTs

  C. Meliani, J. Flucke, A. Wentzel, J. Wurfl, W. Heinrich, G. Trankle
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  ABSTRACT: This paper reports on design and realization of monolithic switch-mode amplifiers for data rates up to 1.8 Gbps, suitable for Class-S and inverse class-D PA modules. GaN HEMT as well as high-voltage GaAs-HBT technologies are employed and compared. For digital signal transmission without output filtering, the chips achieve efficiencies of more than 90% at an output power of 5.4 W and 6.5 W with PAE values including the on-chip drivers, of 75% and 80% for GaAs-HBT and GaN-HEMT Ics respectively. These high efficiencies values are very promising since such PA chips represent the key building block for future class S systems.
  Microwave Symposium Digest, 2008 IEEE MTT-S International; 07/2008
• Article: 5.6-W Broad-Area Lasers With a Vertical Far-Field Angle of 31 Emitting at 670 nm

  B. Sumpf, M. Zorn, M. Maiwald, R. Staske, J. Fricke, P. Ressel, G. Erbert, M. Weyers, G. Trankle
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  ABSTRACT: Highly efficient 670-nm high-power broad-area laser diodes with a single InGaP quantum-well embedded in AlGaInP waveguide layers and n-AlInP and p-AlGaAs cladding layers are presented. The developed vertical layer structure leads to a vertical far-field angle of 31deg. At 15degC, 100 mu-m-wide broad-area lasers reach an output power of 5.6 W limited by thermal rollover. The conversion efficiency was 41% at 1.5 W. A 7600-h reliable operation at 1.5 W and a mean time to failure of about 37550 h will be reported.
  IEEE Photonics Technology Letters 05/2008; · 2.19 Impact Factor
• Article: High pak power femtosecond pulses from modelocked semiconductor laser in external cavity

  T. Schlauch, M. Li, M.R. Hofmann, A. Klehr, G. Erbert, G. Trankle
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  ABSTRACT: The generation of high peak power femtosecond pulses from an all semiconductor laser system is demonstrated. The system is based on a passively modelocked two-section laser diode in an external cavity, a tapered amplifier and a compact external pulse compressor. Pulse durations are achieved below 600 fs with an average optical power above 500 mW at a repetition rate of 330 MHz. This corresponds to a peak power of 2.5 kW, which is the highest value reported for an all semiconductor ultrafast laser system so far.
  Electronics Letters 02/2008; · 0.96 Impact Factor
• Article: High-Power Picosecond Pulse Generation Due to Mode-Locking With a Monolithic 10-mm-Long Four-Section DBR Laser at 920 nm

  S. Schwertfeger, A. Klehr, A. Liero, G. Erbert, G. Trankle
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  ABSTRACT: A 10-mm-long four-section distributed Bragg reflector laser with a double-quantum-well heterostructure at 920 nm was realized. A maximum optical pulse power of 3.6 W with a repetition rate of 4.1 GHz corresponding to the laser length was reached. The full-width at half-maximum of the pulses was 7 ps measured with an autocorrelator. A maximum pulse energy of 25 pJ was reached.
  IEEE Photonics Technology Letters 01/2008; · 2.19 Impact Factor