This research effort advances millimeter-wave transistor modeling in a current RF/Microwave circuit simulator (Agilent's Advanced Design System-ADS) for small-signal noise and large signal simulations. The device modeled is a metamorphic High Electron Mobility Transistor (mHEMT) supplied by Raytheon RF components. Because of their structure, these new low noise devices are used in this work to test the abilities to accurately model in the sub 0.5dB noise figure territory and to study model prediction into W-band (75-110 GHz). New modeling issues discussed in this thesis involve the effects of noise modeling in relation to the small-signal model parameters. The noise modeling identifies two methods of extraction and how to determine good noise data. Other modeling topics addressed are the use of an advanced nonlinear model, and the ability to optimize for gain compression in the nonlinear model. Several measurement systems were used in the extraction and validation of this modeling effort. They consist of the ATN NP5 noise system, Maury Automated Tuner System, Agilent's IC-CAP, and Gateway's Special. The concept behind using these systems was to construct a complete modeling reference for a transistor and validate it against noise parameter and nonlinear measured data. Since the modeling work for this thesis is built on previous work, one goal has been to bring past USF field-effect transistor (FET) modeling efforts up to date and refine them for future use. The noise measurements were compared to results from Raytheon to validate the USF ATN noise parameter measurement system. Also the IC-CAP modeling system has been validated in measuring the test devices using the Maury load-pull system. Small-signal and noise modeling were accomplished using techniques standardized from several technical papers and prior USF Ph.D. work relative to the model extraction. The IC-CAP modeling software also provided a straightforward platform for large-signal model extraction that is documented in this thesis. Using optimization in ADS, a final nonlinear was created. Measured DC, S-parameter, noise parameters, harmonic power, TOI, load-pull, and efficiency measurements were shown to compare well with model data simulated in ADS. Temperature scaling was also executed using a linear approximation of model values over measured temperatures in the noise model. The results presented show that the models developed illustrate good fitting of the behavior of the mHEMT device.

<p> </p><p>As technique and requirement of today’s products keeps expending, Acreo AB has been researching for automotive radar that fulfills these requirements, e.g. higher resolution, faster system and lower cost.</p><p>The purpose of this master thesis work has been to evaluate a previous design and implement changes. The work has resulted in a PCB card that will be used to compare the performance between two radar modules. The demonstrator has been developed in two versions – first based on the existing GaAs-chipset (Gallium Arsenide) and a second with the inclusion of a low cost SiGe-chipset (Silicon Germanium).</p><p>The outcome of this work proves that some requirements cannot be fulfilled and therefore a next-generation radar demonstrator has been proposed. The new radar demonstrator includes changes that can fulfill the requirements.</p><p> </p>

GaAs-based nitride is found to be sensitive to growth conditions and ex-situ annealing processes. The critical thickness is almost one order thicker than the theoretical prediction by force balance model. The growth process could be sped up by the nitrogen incorporation itself, while the nitrogen incorporation could be affected by Beryllium doping. The incorporated nitrogen atoms partly occupy substitutional sites for Arsenic. Some nitrogen atoms are at interstitial sites. Annealing could drastically increase the optical quality of GaAs-based nitrides. As an end of this paper, some preliminary results of InGaAsN/GaAsN/AlGaAs laser diodes are also presented. / Singapore-MIT Alliance (SMA)

GaAs-based InGaAsN/GaAs quantum well is found to be very sensitive to growth conditions and ex-situ annealing processes. Annealing could drastically increase the optical quality of GaAs-based InGaAsN/GaAs quantum well. As an end of this paper, some results on InGaAsN/GaAsN/AlGaAs laser diodes are also presented. / Singapore-MIT Alliance (SMA)

In this article, we report an attempt of extending the InGaAsN materials towards 1.3µm and 1.55µm wavelength. All these InGaAsN samples are grown in a plasma-assisted solid-source molecular-beam epitaxy (SS-MBE) system. Our experiments revealed that the nitrides could be grown with both direct nitrogen beam and dispersive nitrogen. The nitrogen incorporation rate could be reduced by the presence of indium flux. The interaction between nitrogen and indium might lead to 3D growth mode and growth dynamics. It is proved that the increasing growth rate reduces the nitrogen incorporation efficiency. The data for nitrogen sticking coefficient are somewhat contradictive. The growth with dispersive nitrogen source causes the improvement of material quality. Fixed indium flux is a better way for the wavelength control. Also, we report some growth optimization work for better PL property and the annealing effect on the samples. Literature is sometimes reviewed for comparison. / Singapore-MIT Alliance (SMA)

Semi-insulating gallium arsenide (SI-GaAs) has gained great interest in recent years due to its wide application in optoelectronic devices and high-speed integrated circuits. An important feature of SI-GaAs is the high density of deep-level defect states, which control the electrical properties of the substrate by compensating the shallow defects. Over the years, deep-level transient spectroscopy (DLTS) and its variations have been the most effective tools employed for the characterization of deep-level defects. However, most of these techniques require a contact probe and tend to be quite restrictive in their applications’ scope. In this thesis deep-level photo-thermal spectroscopy (DLPTS), an all-optical rate-window-based technique, is presented as a novel noncontact technique for the characterization of deep-level defects in SI-GaAs. The signal-generation mechanism for DLPTS is the super-bandgap excitation of carriers, and the sub-bandgap detection of the defect’s thermal-emission process. Combined with the rate-window detection utilizing lock-in amplifiers, DLPTS measurements are performed in three different modalities: temperature-scan, pulse-rate scan, and time-scan. This work demonstrates that each mode provides unique information about the defect configuration, and, in combination, the modes offer a powerful tool for the study of defect properties and optoelectronic processes in SI-GaAs. A hierarchical carrier-emission theory is proposed to explain the thermal broadening (nonexponentiality) in photo-thermal spectra. The model is studied comparatively with the Gaussian distribution of activation energies, and their similarities demonstrate an ergodic equivalence of random energy distribution and the constrained hierarchical emission process. In addition, a rate-window gated photo-carrier radiometry (PCR) technique is developed. The original diffusion-based PCR theory is modified to reflect the signal domination by trap emission and capture rates in the absence of diffusion. Defect luminescence is collected and analyzed using photo-thermal temperature spectra and resonant detection combined with frequency scans. The study results in the identification of five radiative defect states and the defect-photoluminescence quantum efficiency.

Semi-insulating gallium arsenide (SI-GaAs) has gained great interest in recent years due to its wide application in optoelectronic devices and high-speed integrated circuits. An important feature of SI-GaAs is the high density of deep-level defect states, which control the electrical properties of the substrate by compensating the shallow defects. Over the years, deep-level transient spectroscopy (DLTS) and its variations have been the most effective tools employed for the characterization of deep-level defects. However, most of these techniques require a contact probe and tend to be quite restrictive in their applications’ scope. In this thesis deep-level photo-thermal spectroscopy (DLPTS), an all-optical rate-window-based technique, is presented as a novel noncontact technique for the characterization of deep-level defects in SI-GaAs. The signal-generation mechanism for DLPTS is the super-bandgap excitation of carriers, and the sub-bandgap detection of the defect’s thermal-emission process. Combined with the rate-window detection utilizing lock-in amplifiers, DLPTS measurements are performed in three different modalities: temperature-scan, pulse-rate scan, and time-scan. This work demonstrates that each mode provides unique information about the defect configuration, and, in combination, the modes offer a powerful tool for the study of defect properties and optoelectronic processes in SI-GaAs. A hierarchical carrier-emission theory is proposed to explain the thermal broadening (nonexponentiality) in photo-thermal spectra. The model is studied comparatively with the Gaussian distribution of activation energies, and their similarities demonstrate an ergodic equivalence of random energy distribution and the constrained hierarchical emission process. In addition, a rate-window gated photo-carrier radiometry (PCR) technique is developed. The original diffusion-based PCR theory is modified to reflect the signal domination by trap emission and capture rates in the absence of diffusion. Defect luminescence is collected and analyzed using photo-thermal temperature spectra and resonant detection combined with frequency scans. The study results in the identification of five radiative defect states and the defect-photoluminescence quantum efficiency.

As technique and requirement of today’s products keeps expending, Acreo AB has been researching for automotive radar that fulfills these requirements, e.g. higher resolution, faster system and lower cost. The purpose of this master thesis work has been to evaluate a previous design and implement changes. The work has resulted in a PCB card that will be used to compare the performance between two radar modules. The demonstrator has been developed in two versions – first based on the existing GaAs-chipset (Gallium Arsenide) and a second with the inclusion of a low cost SiGe-chipset (Silicon Germanium). The outcome of this work proves that some requirements cannot be fulfilled and therefore a next-generation radar demonstrator has been proposed. The new radar demonstrator includes changes that can fulfill the requirements.

The purpose of this thesis is to fabricate 12-layer In0.75Ga0.25As quantum dot-in-a-well (In0.1Ga0.9As) structures grown by molecular-beam epitaxy (MBE) on GaAs substrate, and analyze the optical properties of laser devices for optical fiber communication systems. For the laser structures, larger Al content AlGaAs cladding layer enhance the optical confinement, but encounter much challenges to improve the quality. After we simulate and fabricate different Al content laser structures, we find the best cladding layer composition - Al0.2Ga0.8As which performs a best material gain. In the active layer, 12 layers In0.75Ga0.25As quantum dots (QDs) and QDs in a well (DWell) structure, and DWell with Be-doping in the well structure are included in this study. The well structure slows down the hot carriers speed and Be-doping decrease the carrier life time and increases the electron-hole pair recombination rate. We increase the QDs deposition coverage to move the emission wavelength to 1.3£gm, but the high temperature cladding layer growth process indirectly anneal the QDs and result in the emission wavelength blue shift to 1.24£gm. In the laser fabrication, to transport the light wave in smaller dispersion loss single mode waveguide, wet etching photolithography processes are adapted in this study to fabricate 2£gm width ridge waveguide. The as-cleaved facets are used as Fabry-Perot laser mirrors in ridge waveguide lasers. Finally, the current density of QD Laser(C528) lasing in CW mode is 581A/cm2, slope efficiency of 510mW/A and maximum power/facet of 65mW are obtained.Then the current density of DWELL+PD Laser(C540) lasing in CW mode is 880A/cm2, slope efficiency of 430mW/A and maximum power/facet of 34mW are obtained.

The purpose of this thesis is to fabricate 12-layer InxGa1-xAs quantum dots grown on 2-nm In0.1Ga0.9As quantum wells (DWell) laser structures grown by molecular-beam epitaxy (MBE) on GaAs substrats. We expect to optimum the lasers performance by tune the epitaxial recipe and fabrication condition. For the carrier injection efficiency, DWell structure of quantum dots grown on quantum wells is proposed to enhance the carrier capture rate. So we analyze a series of DWell structure in this work. In the epitaxial recipe, we investigate the influences of p-type doping and change the quantum wells growth temperature for the laser structures. In the laser fabrication, to transport the light wave in smaller dispersion loss single mode waveguide, dry etching photolithography processes are adapted in this study to fabricate 2.2mm width ridge waveguide. The as-cleaved facets are used as Fabry-Perot laser mirrors in ridge waveguide lasers. The pattern can be transferred effectively with less under-cut by dry etching compare with wet etching. Finally, the P-type doping DWell laser exhibits high power/facet of 24mW, slope efficiency of 0.209W/A. The maximum power/facet of PWell580 laser reach to 24mW, slope efficiency of 0.238W/A after raising the growth temperature to 580oC.