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A GaN based highly integrated Solid State Power Amplifier (SSPA) is developed for S-band radar applications. The power amplifier delivers more than 1 KW within a 400 MHz bandwidth with 55 dB gain and a typical 34% PAE. The SSPA includes a negative voltage supply, sequential bias circuit, and temperature sensor circuit. Its compact and lightweight design is suitable for many radar applications.
We have developed a thermal analysis methodology, packaging design process and validation procedure demonstrating that GaN power amplifiers, having greater than 100W of RF output power, can be managed thermally in practical higher level assemblies. Microscopic and macroscopic models were used to evaluate performance. Novel thermal dissipation test structures were designed, fabricated and measured...
A high efficient GaN switch-mode amplifier for Gbit data rates is presented. The design uses GaN HEMTs with a gate length of 250 nm. It consists of a dual-gate transistor configuration in the output stage. This allows an increase of supply voltage in order to increase the output power. If an increase of power is not required, device size can be reduced which comes along with a better RF-performance...
In this paper, we employ a novel method by using resonators with microstrip lines to design a dual-band GaN HEMT power amplifier. At both input and output matching networks, we add parallel resonators between series microstrip lines and open-circuited stubs to realize the dual-band operation. With our proposed structure, we can use the conventional L-type structure to design matching network for each...
This paper reports the design, implementation, and experimental results of two high efficiency GaN-HEMT power amplifiers (PAs) at 3.5 GHz and 5.5 GHz. A bare-die approach is used to eliminate package parasitics in conjunction with an in-house transistor model that enables investigation of the transistor intrinsic waveforms. With this as a basis, harmonic source-pull/load-pull simulations have been...
In this paper, we present a successful operation of Gallium Nitride(GaN)-based three-phase inverter with high efficiency of 99.3% for driving motor at 900W under the carrier frequency of 6kHz. This efficiency well exceeds the value by IGBT (Insulated Gate Bipolar Transistor). This demonstrates that GaN has a great potential for power switching application competing with SiC. Fully reduced on-state...
In many communications applications semiconductor devices operate in a pulsed mode, where rapid temperature transients are continuously experienced within the die. We proposed a novel junction-level cooling technology where a metallic phase change material (PCM) was embedded in close proximity to the active transistor channels without interfering with the device's electrical response. Here we present...
We report the epitaxial growth, fabrication, electrical and optical characteristics of GaN/AlGaN p-i-n avalanche photodiodes. The effects of polarization charge density on the dark current and the spectral responsivity of GaN/AlGaN p-i-n avalanche photodiodes are investigated in detail.
A novel thermal management technology was explored to lower the peak temperature associated with high power GaN transistors in pulse application. The technology involves the use of an embedded microscale PCM heat storage device within the chip (near the active channels of the GaN device), which effectively increases the heat capacity of the material by taking advantage of the latent heat of the PCM...
An analytical dc model is presented for amorphous In-Ga-Zn-Oxide (a-IGZO) thin film transistors on the basis of surface potential calculation by Lambert W equation, assuming an exponential trap states density within the bandgap. Charge sheet approximation is utilized to derive the trapped and free charges. The model results are compared with experimental data and a good agreement is achieved.
The carrier transport properties of AlGaN/GaN/InGaN/GaN double-heterojunction HEMTs (DH-HEMTs) have been investigated. Previous hydrodynamic model exhibits significant discrepancies with the experimental results when used for simulating electrical properties of these DH-HEMTs. With the modification of low field mobility by taking into consideration several scattering mechanisms at InGaN/GaN interface,...
This paper presents an analysis of the noise spectra of GaAs and GaN Schottky barrier diodes (SBD) operating under static and time varying conditions. The noise spectra obtained from Monte Carlo simulations (MC) of the SBDs show two resonances in the terahertz frequency region that are analyzed as a function of the SBD structure and working conditions. MC simulations are compared with published analytical...
The temperature impact on the Ohmic contact to Gallium Nitride (GaN) device properties is investigated in the range of 25°C to 300°C by means of the Transmission Line Method (TLM) technique. This study is centered in two kinds of Ohmic contacts: Implanted N+ GaN and heterojunction AlGaN/GaN contacts. For N+ contact resistance behavior is explained in terms of the field-effect or thermionic field effect...
At very low temperature, when optical phonon emission is the dominant scattering mechanism, the phenomenon known as Optical Phonon Transit Time Resonance (OPTTR) may originate current oscillations in n+ nn+ diodes at frequencies in the terahertz range. In this work, by means of Monte Carlo simulations, we study the optimum conditions for the onset of such mechanism in GaN diodes. For this purpose,...
This paper presents a theoretical study of the performance of GaN-based avalanche photodetectors using an ensemble Monte Carlo method. The model includes the details of the full band structure derived from nonlocal empirical pseudopotential calculations. Carrier-phonon and impact ionization scattering rates are obtained from the calculated electronic structure and from a first-principles study of...
GaN nanorod arrays are grown by selective area growth. The exposed nonpolar planes of the nanostructures can be utilized as a potential solution to improve the efficiency of light emitting diodes.
This work discusses wideband high efficiency envelope tracking (ET) power amplifiers using GaN high electron mobility transistors (HEMTs) to achieve high gain and high efficiency with good linearity. The performances of two ET amplifiers using the same GaN RF device and envelope voltages of 30-V peak and 45-V peak are compared experimentally. With the higher dynamic voltage swing (45-V case), a considerably...
A thermal imaging technique is used to characterize a Monolithic Gallium Nitride distributed power amplifier under DC and RF drive conditions. The temperature difference among the active cells (transistors) in distributed power amplifier is observed under RF drive conditions. It is believed that this non-uniform performance of individual cells in broadband distributed power amplifier results in its...
The design and implementation of a high efficiency Class-J power amplifier (PA) for base station applications is reported. A commercially available 10 W GaN HEMT device was used, for which a large-signal model and an extrinsic parasitic model were available. Following Class-J theory, the needed harmonic terminations at the output of the transistor were defined and realised. Experimental results show...
This paper presents a 1.5 bit (3-level) envelope amplifier to improve the overall efficiency of wideband high linearity envelope tracking power amplifier. The proposed envelope amplifier has been devised with two switches providing the different supply voltages. Since the unnecessary current (ripple current) induced by a switching stage can be reduced by the multi-level quantization, the efficiency...
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