Thesis (Ph. D.)--Oregon Graduate Institute of Science & Technology, 1994.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Cressler, John; Committee Member: Laskar, Joy; Committee Member: Papapolymerou, John. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

No description available.

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A more complete model for InP/InGaAs Double Heterojunction Bipolar Transistors (DHBT) is obtained in this thesis by physically analyzing the transport process of the main current components. The potential distribution of the energy barrier constitutes a fundamental analytical concept and is employed for applying the diffusion, the thermionic emission, and the tunneling theories in investigating the injection mechanisms at the e-b heterojunction interface. The diffusion transport is considered first for electron injection from the emitter into the base. The thermionic emission is applied properly at the point of maximum potential energy as one of the boundary conditions at that interface. A suitable energy level is selected with respect to which the energy barrier expression is expanded for the calculation of the tunneling probability. The first "spike" at the conduction band discontinuity is described as the potential energy for the injected electrons to obtain kinetic energy to move into the base region with a substantially high Velocity. The electron blocking action of the second "spike" at the b–c junction is also analyzed by considering the transport Velocity with which electrons are swept out of that boundary. Based on the material parameters recently reported for both InP and InGaAs, computations of the nI current components are carried out to provide à characteristics in good agreement with the reported experimental results. / Master of Science

The design and development of computer models to simulate analog devices and their effects on circuit applications has been investigated at length. The focus of this research is the development of theoretical and computer models for discrete devices using the popular simulator PRECISE, PRogram for Evaluating Circuits in an Interactive Simulation Environment [3], using a new method for model construction. This new method develops a model approximating the mathematics of the simulation via perturbations and iterations [19]. The models developed by the new method in each case yield a minimum simulation accuracy of 90 percent in circuit applications. In comparison, models developed by the conventional method, which uses measured data to complete physical constructs of SPICE 2G.6 [5], offer a lower accuracy for the same circuits. Hence, the new method is more effective than the old method and also much faster, since the model generation process is now automated and does not require time-consuming manual measurements and calculations spread out over a long period of time. With further development, a computer model can also be developed for the theoretical model presented in this thesis for the Gallium Arsenide Metal Semiconductor Field Effect Transistor (GaAs MESFET) device using the same methodology that has been used to develop the computer model for the Bipolar Junction Transistor (BUT) device. Hence this research, in addition to developing a library of a hundred and fifty odd successful models in the PRECISE and SPICE formats for the diode and BUT, can also be used to develop a new model for the GaAs MESFET, which would make both PRECISE and SPICE easier and more user friendly as circuit simulators. / Master of Science

It is proposed to represent a nonlinear two-port device by a scattering parameter (S-parameter) model containing a single nonlinearity. Furthermore, it is proposed that the nonlinearity be modeled as a memoryless nonlinear function. A bipolar junction transistor (BJT) operating in the active region is suggested as one application of this modeling approach. The validity of the model is demonstrated by the comparison of measured and model-predicted data for a microwave BJT. The proposed nonlinear model is represented by a linear three-port flowgraph having one of its ports terminated in a real-valued, nonlinear reflection. The model parameters are determined from measurements of device-under-test (DUT) transmission and reflection at various input drive levels. As an illustration of its utility, the model is applied to the design of an oscillator. The measured results of a constructed oscillator are provided. A presentation of a new form of calibration for microwave measurement systems precedes the nonlinear modeling discussion. The new calibration technique combines the transmission line approach to calibration with a load-pull process common to nonlinear device measurements. A two-port, one-way measurement process obviates the need for DUT reversal. The calibrated measurement of input reflection, transmission, and load reflection is discussed. In addition, the procedure for determining the small-signal S parameters of the DUT is given. / Master of Science

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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 (ɳi) 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/cm², and power density > 3.05 MW/cm² are achieved at RT, which are all the highest values reported ever on III-N HBTs.