223 research outputs found

    Assessment of thermal instabilities and oscillations in multifinger heterojunction bipolar transistors through a harmonic-balance-based CAD-oriented dynamic stability analysis technique

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    We present a novel analysis of thermal instabilities and oscillations in multifinger heterojunction bipolar transistors (HBTs), based on a harmonic-balance computer-aided-design (CAD)-oriented approach to the dynamic stability assessment. The stability analysis is carried out in time-periodic dynamic conditions by calculating the Floquet multipliers of the limit cycle representing the HBT working point. Such a computation is performed directly in the frequency domain, on the basis of the Jacobian of the harmonic-balance problem yielding the limit cycle. The corresponding stability assessment is rigorous, and the efficient calculation method makes it readily implementable in CAD tools, thus allowing for circuit and device optimization. Results on three- and four-finger layouts are presented, including closed-form oscillation criteria for two-finger device

    When self-consistency makes a difference

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    Compound semiconductor power RF and microwave device modeling requires, in many cases, the use of selfconsistent electrothermal equivalent circuits. The slow thermal dynamics and the thermal nonlinearity should be accurately included in the model; otherwise, some response features subtly related to the detailed frequency behavior of the slow thermal dynamics would be inaccurately reproduced or completely distorted. In this contribution we show two examples, concerning current collapse in HBTs and modeling of IMPs in GaN HEMTs. Accurate thermal modeling is proved to be be made compatible with circuit-oriented CAD tools through a proper choice of system-level approximations; in the discussion we exploit a Wiener approach, but of course the strategy should be tailored to the specific problem under consideratio

    When self-consistency makes a difference

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    Compound semiconductor power RF and microwave device modeling requires, in many cases, the use of selfconsistent electrothermal equivalent circuits. The slow thermal dynamics and the thermal nonlinearity should be accurately included in the model; otherwise, some response features subtly related to the detailed frequency behavior of the slow thermal dynamics would be inaccurately reproduced or completely distorted. In this contribution we show two examples, concerning current collapse in HBTs and modeling of IMPs in GaN HEMTs. Accurate thermal modeling is proved to be be made compatible with circuit-oriented CAD tools through a proper choice of system-level approximations; in the discussion we exploit a Wiener approach, but of course the strategy should be tailored to the specific problem under consideration

    Microwave and Millimeter-Wave Signal Power Generation

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    Thermal Design of Power Semiconductor Modules for Mobile Communication Systems

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    We will describe the thermal performance of power semiconductor module, which consists of hetero-junction bipolar transistors (HBTs), for mobile communication systems. We calculate the thermal resistance between the HBT fingers and the bottom surface of a multi-layer printed circuit board (PCB) using a finite element method (FEM). We applied a steady state analysis to evaluate the influence of design parameters on thermal resistance of the module. We found that the thickness of GaAs substrate, the thickness of multi-layer circuit board, the thermal conductivity of bonding material under GaAs substrate, and misalignment of thermal vias between each layer of PCB are the dominant parameter in thermal resistance of the module.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

    Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors

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    This dissertation describes the development of III-nitride (III-N) bipolar devices for optoelectronic and electronic applications. Research mainly involves device design, fabrication process development, and device characterization for Geiger-mode gallium nitride (GaN) deep-UV (DUV) p-i-n avalanche photodiodes (APDs), indium gallium nitride (InGaN)/GaN-based violet/blue laser diodes (LDs), and GaN/InGaN-based npn radio-frequency (RF) double-heterojunction bipolar transistors (DHBTs). All the epitaxial materials of these devices were grown in the Advanced Materials and Devices Group (AMDG) led by Prof. Russell D. Dupuis at the Georgia Institute of Technology using the metalorganic chemical vapor deposition (MOCVD) technique. Geiger-mode GaN p-i-n APDs have important applications in DUV and UV single-photon detections. In the fabrication of GaN p-i-n APDs, the major technical challenge is the sidewall leakage current. To address this issue, two surface leakage reduction schemes have been developed: a wet-etching surface treatment technique to recover the dry-etching-induced surface damage, and a ledged structure to form a surface depletion layer to partially passivate the sidewall. The first Geiger-mode DUV GaN p-i-n APD on a free-standing (FS) c-plane GaN substrate has been demonstrated. InGaN/GaN-based violet/blue/green LDs are the coherent light sources for high-density optical storage systems and the next-generation full-color LD display systems. The design of InGaN/GaN LDs has several challenges, such as the quantum-confined stark effect (QCSE), the efficiency droop issue, and the optical confinement design optimization. In this dissertation, a step-graded electron-blocking layer (EBL) is studied to address the efficiency droop issue. Enhanced internal quantum efficiency (Éłi) has been observed on 420-nm InGaN/GaN-based LDs. Moreover, an InGaN waveguide design is implemented, and the continuous-wave (CW)-mode operation on 460-nm InGaN/GaN-based LDs is achieved at room temperature (RT). III-N HBTs are promising devices for the next-generation RF and power electronics because of their advantages of high breakdown voltages, high power handling capability, and high-temperature and harsh-environment operation stability. One of the major technical challenges to fabricate high-performance RF III-N HBTs is to suppress the base surface recombination current on the extrinsic base region. The wet-etching surface treatment has also been employed to lower the surface recombination current. As a result, a record small-signal current gain (hfe) > 100 is achieved on GaN/InGaN-based npn DHBTs on sapphire substrates. A cut-off frequency (fT) > 5.3 GHz and a maximum oscillation frequency (fmax) > 1.3 GHz are also demonstrated for the first time. Furthermore, A FS c-plane GaN substrate with low epitaxial defect density and good thermal dissipation ability is used for reduced base bulk recombination current. The hfe > 115, collector current density (JC) > 141 kA/cmÂČ, and power density > 3.05 MW/cmÂČ are achieved at RT, which are all the highest values reported ever on III-N HBTs.PhDCommittee Chair: Shen, Shyh-Chiang; Committee Member: Dupuis, Russell; Committee Member: Jiang, Zhigang; Committee Member: Mukhopadhyay, Saibal; Committee Member: Yoder, Dougla

    Characterization of intra device mutual thermal coupling in multi finger SiGe:C HBTs

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    This paper studies the mutual coupling in trench isolated multi emitter bipolar transistors fabricated in a Si/SiGe:C HBT technology STMicroelectronics featuring fT and fmax of ~300GHz and ~400GHz, respectively. Thermal coupling parameters are extracted using three dimensional (3D) thermal TCAD simulations. The obtained parameters are implemented in a distributed transistor model that considers self-heating as well as thermal coupling between emitter fingers. Very good agreement is achieved between circuit simulations and DC measurements carried out on an in house designed test structure.Comment: Preprint, submitted to EDSSC 201

    Effective electrothermal analysis of electronic devices and systems with parameterized macromodeling

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    We propose a parameterized macromodeling methodology to effectively and accurately carry out dynamic electrothermal (ET) simulations of electronic components and systems, while taking into account the influence of key design parameters on the system behavior. In order to improve the accuracy and to reduce the number of computationally expensive thermal simulations needed for the macromodel generation, a decomposition of the frequency-domain data samples of the thermal impedance matrix is proposed. The approach is applied to study the impact of layout variations on the dynamic ET behavior of a state-of-the-art 8-finger AlGaN/GaN high-electron mobility transistor grown on a SiC substrate. The simulation results confirm the high accuracy and computational gain obtained using parameterized macromodels instead of a standard method based on iterative complete numerical analysis

    Design of SiGe HBT power amplifiers for microwave radar applications

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    A novel modification to the standard cascode amplifier architecture is presented in SiGe which allows for an optimal separation of gain and breakdown functions through the mixed breakdown cascade architecture, opening the door for moderate power amplifiers in SiGe. Utilizing this technique, a two-stage, high-gain amplifier operating at X-Band is fabricated and measured. The 20 dB of gain per stage represents the highest gain at X-Band at the time of publication. Additionally, a near one Watt power amplifier is designed and fabricated at X-Band, which represents the highest output power in SiGe at X-Band at time of publication. Related to the power amplifier design, thermal considerations are also investigated. The validity of utilizing lumped mutual thermal coupling in SiGe devices is presented. Using this finding, a thermal coupling model and network which are compliant for use with commonly available HBT models and circuit simulators is presented. This model and network is used to thermally optimize SiGe PA cells based upon layout spacing.Ph.D.Committee Member: John Cressler; Committee Member: John Papapolymerou; Committee Member: Joy Laskar; Committee Member: Thomas Morley; Committee Member: William Hun
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