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  • 1. Akram, Muhammad Nadeem
    et al.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Influence of base-region thickness on the performance of Pnp transistor-VCSEL2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 22, p. 27398-27414Article in journal (Refereed)
    Abstract [en]

    We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surface-emitting laser (TVCSEL) operating at room temperature with optical power up to 1.8mW. However, the current gain beta = Delta I-c/Delta I-b was near zero just before lasing and became negative after the lasing threshold. The main cause of the negative current gain was found to be a gradual and position-dependent forward-biasing (saturation) of the base-collector junction with increasing bias even before lasing threshold. In this article, detailed multi-physics device simulations are performed to better understand the device physics, and find ways to avoid the premature saturation of the base-collector junction. We have optimized the thickness of the base region as well as its doping concentration and the location of the quantum wells to ensure that the T-VCSEL is in the active mode throughout its range of operation. That is, the emitter-base junction is forward biased and base-collector junction is reversed biased for sweeping the excess charges out of the base region.

  • 2.
    Hammar, Mattias
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, M. N.
    Room-temperature operation of 980-nm transistor-vertical-cavity surface-emitting lasers2013In: 2013 IEEE 6th International Conference on Advanced Infocomm Technology, ICAIT 2013, IEEE , 2013, p. 141-142Conference paper (Refereed)
    Abstract [en]

    We report on the design, fabrication and characterization of pnp-type 980-nm transistor-vertical-cavity surface-emitting lasers (T-VCSELs). Using an epitaxial regrowth process and a triple-intracavity current injection scheme we demonstrate static performance levels quite comparable to those of conventional VCSELs, including sub-mA threshold base current, mW-range output power and continuous-wave operation at least up to 50°C.

  • 3.
    Junesand, Carl
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Gau, Ming-Horng
    KTH, School of Information and Communication Technology (ICT).
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Heterogeneous integration of indium phosphide on silicon by nano-epitaxial lateral overgrowth2009In: 2009 IEEE 21ST INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM), 2009, p. 59-62Conference paper (Refereed)
    Abstract [en]

    InP on Si is grown by nano-epitaxial lateral overgrowth (nano-ELOG) on patterns consisting of net-type openings under different growth conditions. Analysis shows that net-type patterns yield large lateral growth rate and good optical quality. Different growth conditions have a substantial impact on growth rate and some effect on surface morphology, as well as on the optical quality. Optical quality is deemed to be affected partly by the amount of dislocations arising from the difference in thermal expansion coefficient between the mask and the InP layer, and partly by the layer thickness and surface morphology.

  • 4.
    Junesand, Carl
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Gau, Ming-Horng
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Surface morphology of indium phosphide grown on silicon by nano-epitaxial lateral overgrowth2009In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 6, no 12, p. 2785-2788Article in journal (Refereed)
    Abstract [en]

    InP is grown on Si by nano-epitaxial lateral overgrowth (NELOG or nano-ELOG) on patterns consisting of net-type openings under different growth conditions. Surface morphology is characterized with AFM and profilometer and optical quality assessed by Micro Photoluminescence measurements (mu-PL). Results show that growth conditions affect both morphology and optical quality, with thicker layers generally corresponding to better surface morphology. Lower growth temperature seems to improve surface morphology irrespective of thickness, and ELOG layers exhibit significantly better morphology than the planar layer.

  • 5. Shi, W.
    et al.
    Faraji, B.
    Greenberg, M.
    Berggren, Jesper
    Department of Electrical and Computer Engineering, University of British Columbia.
    Xiang, Yu
    Department of Electrical and Computer Engineering, University of British Columbia.
    Hammar, Mattias
    Department of Electrical and Computer Engineering, University of British Columbia.
    Chrostowski, L.
    Self-consistent modeling of a transistor vertical-cavity surface-emitting laser2010In: 10th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2010, 2010, p. 45-46Conference paper (Refereed)
    Abstract [en]

    A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The quantum capture/escape process is simulated using a quantum-trap model. Both the steady state and frequency response of the T-VCSEL are calculated by a numerical and analytical approach.

  • 6. Shi, Wei
    et al.
    Faraji, Behnam
    Greenberg, Mark
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Lestrade, Michel
    Li, Zhi-Qiang
    Li, Z. M. Simon
    Chrostowski, Lukas
    Invited Paper: Design and modeling of a transistor vertical-cavity surface-emitting laser2011In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 42, no 11-13, p. 659-666Article in journal (Refereed)
    Abstract [en]

    A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The important physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a significant effect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the analytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.

  • 7.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    GaAs based Vertical-Cavity Surface-Emitting Transistor-Lasers2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The ever-increasing demand for broadband capacity of the global optical communication networks puts enormous requirements on the semiconductor laser used in the optical transmitter. Industrial standard bodies for optical communication project requirements of single-channel data rates as high as 100 Gbit/s around year 2020. This is a significant step with respect to today's technology which is only at the verge of introducing 25 Gbit/s emitters. The preferred light source for these applications is the vertical-cavity surface-emitting laser (VCSEL) which can offer cost- and power-efficient directly modulated operation. However, it has proven extremely difficult to push the modulation bandwidth of VCSELs beyond 30 GHz and radically new device concepts are demanded to meet the upcoming needs. One such new device paradigm consists of the transistor laser which is the fusion of a semiconductor laser and a high-speed heterojunction bipolar transistor (HBT) into a single device, with potential significant advantages in modulation bandwidth, noise properties and novel functionality by virtue of the three-terminal configuration. The present thesis deals with the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs), a device previously not realized or investigated in great detail.

    GaAs-based T-VCSELs are investigated both theoretically and experimentally. A three-dimensional model is set up with a commercial software package and used for performance predictions and analysis as well as design and optimization purposes. It is concluded that a T-VCSEL biased in the common-base configuration may have a bandwidth surpassing those of conventional diode-type VCSELs or a T-VCSEL itself in the common-emitter configuration. Fabricated T-VCSELs make use of an epitaxial regrowth design to homogeneously integrate an AlGaAs/GaAs HBT and an InGaAs/GaAs VCSEL. An intracavity contacting scheme involving all three terminals, undoped distributed Bragg reflectors and modulation doping are used to ensure a low-loss laser structure. The first generation of devices showed sub-mA range base threshold current in combination with a high output power close to 2 mW but did not fulfill the requirements for a fully operational transistor laser since the transistor went into saturation before the onset of lasing (IBsat<IBth). From numerical simulations this premature saturation was demonstrated being due to a lateral potential variation within the device and large voltage drops along the base and collector regions. As a remedy to this problem the base region was redesigned for a reduced resistance and transistor current gain, and the saturation current could thereby be extended well beyond threshold. These devices showed excellent transistor-laser characteristics with clear gain-compression at threshold, mA-range base threshold current, mW-range output power, high-temperature operation to at least 60°C, low collector-emitter offset voltage and record-low power dissipation during lasing. Furthermore, the collector-current breakdown characteristics was investigated in some detail and it is concluded that this, in contrast to previous models, presumably not is due to an intracavity photon reabsorption process but rather to a quantum-well band-filling effect.

  • 8.
    Xiang, Yu
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yang, Chen
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasersManuscript (preprint) (Other academic)
    Abstract [en]

    We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60°C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection to improve the lateral feeding.

  • 9.
    Xiang, Yu
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yang, Chen
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, M. N.
    AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers2015In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, no 12, p. 15680-15699Article in journal (Refereed)
    Abstract [en]

    We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60 degrees C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection for reduced extrinsic resistances.

  • 10.
    Xiang, Yu
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yang, Chen
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, Muhammed Nadeem
    University Collage of Buskerud and Vestfold.
    Performance Optimization of GaAs-Based Vertical-Cavity Surface-Emitting Transistor-Lasers2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 7, p. 721-724Article in journal (Refereed)
    Abstract [en]

    We report on the optimization of pnp-type verticalcavity surface-emitting transistor-lasers based on the fusion between an AlGaAs/GaAs heterojunction bipolar transistor and an InGaAs/GaAs VCSEL using an epitaxial regrowth process. It is shown how a proper design of the base region can extend the transistor active range of operation well beyond lasing threshold, thereby resulting in typical transistor laser operational characteristics including mW-range output power, mA-range base threshold current, record-low power dissipation under laser operation, and continuous-wave operation up to at least 60°C. A pronounced breakdown in the collector current characteristics in the limit of high base current and/or emitter-collector voltage accompanied by a quenching of the optical output power is interpreted as being related to quantum well band-filling.

  • 11.
    Xiang, Yu
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, Muhammed Nadeem
    University Collage Vestfold.
    Minority current distribution in InGaAs/GaAs transistor-vertical-cavity surface-emitting laser2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 19, p. 191101-Article in journal (Refereed)
    Abstract [en]

    We compare experimental data with three-dimensional numerical calculations of the local minority current in an InGaAs/GaAs transistor vertical-cavity surface-emitting laser at different bias levels. It is demonstrated that lateral potential variations within the device greatly affect the transistor operating conditions. As a result, it locally operates in the active mode in the center of the device, allowing for efficient stimulated recombination, while it globally operates in the saturation regime as reflected by the measured current-voltage characteristics. This allows for excellent laser performance, including mW-range output power, sub-mA threshold base current, and continuous-wave operation well above room temperature.

  • 12.
    Yu, Xingang
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Chung, Il-Sug
    Mork, Jesper
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Single-mode InGaAs/GaAs 1.3-mu m VCSELs Based on a Shallow Intracavity Patterning2010In: SEMICONDUCTOR LASERS AND LASER DYNAMICS IV / [ed] Panajotov, K; Sciamanna, M; Valle, AA; Michalzik, R, 2010, Vol. 7720, p. 772021-Conference paper (Refereed)
    Abstract [en]

    A high-power single-mode 1.3-mu m InGaAs/GaAs vertical-cavity surface-emitting laser (VCSEL) structure employing a novel concept of engineering the optical mode profile to match the gain profile is suggested and demonstrated experimentally and theoretically. In contrast to various singlemode VCSEL approaches reported in the literature so far, based on selective loss or anti-resonant effects to suppress higher order modes, it is due to a novel design to increase the active region size while maintaining single mode emission. The shape of the fundamental mode profile is engineered to be similar to the gain profile which resembles a doughnut shape especially in intra-cavity contacted devices. In this way, the fundamental mode with the best fit to the gain profile can reach the lasing condition earliest and consume all the optical gain, leading to a suppression of higher order modes. Notably, despite this engineered shape of the mode profile, the far field shape remains close to Gaussian. The mode shaping can be achieved by introducing a shallow intracavity patterning before depositing the top mirror. Fabricated device structures consist of a A-Si/SiN/SiO(2) top mirror, modulation-doped current spreading layers, re-grown current confinement layers, three InGaAs/GaAs quantum wells, and a GaAs/AlGaAs bottom mirror. Single mode operation is demonstrated even for devices with active region as large as 10 mu m.

  • 13.
    Yu, Xingang
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, Muhammad Nadeem
    Vestfold University Collage, Tönsberg, Norge.
    Shi, Wei
    University of British Columbia, Vancouver, Canada.
    Chrostowski, Lukas
    University of British Columbia, Vancouver, Canade.
    Room-temperature operation of transistor vertical-cavity surface-emitting laser2013In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 49, no 3, p. 208-209Article in journal (Refereed)
    Abstract [en]

    The first room-temperature operation of a transistor vertical-cavity surface-emitting laser (T-VCSEL) is demonstrated. Fabricated using an epitaxial regrowth process, the T-VCSEL is electrically a pnp-type bipolar junction transistor and consists of an undoped AlGaAs/GaAs bottom DBR, an InGaAs triple-quantum-well active layer, an Si/SiO2 dielectric top DBR, and an intracavity contacting scheme with three electrical terminals. The output power is controlled by the base current in combination with the emitter-collector voltage, showing a voltage-controlled operation mode. A low threshold base-current of 0.8 mA and an output power of 1.8 mW have been obtained at room temperature. Continuous-wave operation was performed up to 50 degrees C.

  • 14.
    Yu, Xingang
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Xiang, Yu
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    1.3 μm Buried Tunnel junction InGaAs/GaAs VCSELs2013Conference paper (Other academic)
    Abstract [en]

    Vertical cavity surface emitting lasers (VCSELs) working at 1.3μm are potential cost- and power-efficient sources for medium-range optical networks. However, they are still waiting for their commercial breakthrough due to several technological challenges related to the need for complex materials systems and/or fabrication methods. Nevertheless, many efforts have been devoted to solve the problem, also yielding some excellent results. Alter-native approaches we have previously presented are In-GaAs/GaAs 1.3-μm VCSELs based on oxidation con-finement or with an epitaxial regrowth of a pnp block-ing structure. Here we demonstrate a buried-tunnel junction (BTJ) current confinement scheme to improve the static and dynamic performance.

1 - 14 of 14
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