Dual-Band, Dual-Output Power Amplifier Using Simplified Three-Port, Frequency-Dividing Matching Network

This study presents a dual-band power amplifier (PA) with two output ports using a simplified three-port, frequency-dividing matching network. The dual-band, dual-output PA could amplify a dual-band signal with one transistor, and the diplexer-like output matching network (OMN) divided the two bands into different output ports. A structure consisting of a λ/4 open stub and a λ/4 transmission line was applied to restrain undesired signals, which made each branch equivalent to an open circuit at another frequency. A three-stub design reduced the complexity of the OMN. Second-order harmonic impedances were tuned for better efficiency. The PA was designed with a 10-W gallium nitride high electron mobility transistor (GaN HEMT). It achieved a drain efficiency (DE) of 55.84% and 53.77%, with the corresponding output power of 40.22 and 40.77 dBm at 3.5 and 5.0 GHz, respectively. The 40%-DE bandwidths were over 200 MHz in the two bands.

Optimization based on electro-thermo-mechanical modeling of the high electron mobility transistor (HEMT)

The electro-thermomechanical modeling study of the High Electron Mobility Transistor (HEMT) has been presented, all the necessary equations are detailed and coupled. This proposed modeling by the finite element method using the Comsol multiphysics software, allowed to study the multiphysics behaviour of the transistor and to observe the different degradations in the structure of the component. Then, an optimization study is necessary to avoid failures in the transistor. In this work, we have used the Covariance Matrix Adaptation-Evolution Strategy (CMA-ES) method to solve the optimization problem, but it requires a very important computing time. Therefore, we proposed the kriging assisted CMA-ES method (KA-CMA-ES), it is an integration of the kriging metamodel in the CMA-ES method, it allows us to solve the problem of optimization and overcome the constraint of calculation time. All these methods are well detailed in this paper. The coupling of the finite element model developed on Comsol Multiphysics and the KA-CMA-ES method on Matlab software, allowed to optimize the multiphysics behaviour of the transistors. We made a comparison between the results of the numerical simulations of the initial state and the optimal state of the component. It was found that the proposed KA-CMA-ES method is efficient in solving optimization problems.

Analytical Study of ZnO-based HEMT for Power Switching

We investigate the power switching mechanism to evaluate the power loss ( P D ) and efficiency ( η ) in MgZnO/ZnO (MZO)-based power high electron mobility transistor (HEMT), and physical parameters responsible for P D in molecular beam epitaxy (MBE) and dual ion beam sputtering (DIBS) grown MZO HEMT and compare the performance with the group III-nitride HEMTs. This work extensively probes all physical parameters such as two-dimensional electron gas (2DEG) density, mobility, switching frequency, and device dimension to study their impact on power switching in MZO HEMT. Results suggest that the MBE and DIBS grown MZO HEMT with the gate width ( W G ) of ∼ 205 and ∼ 280 mm at drain current coefficient (k) of 11 and 15, respectively, will achieve 99.96 and 99.95% of η and 9.03 and 12.53 W of P D , respectively. Moreover, W G value for DIBS-grown MZO HEMT is observed to further reduce in the range of 112-168 mm by using a Y 2 O 3 spacer layer leading to the maximum η in the range of 99.98-99.97% and the minimum P D in the range of 5-7 W. This work is significant for the development of cost-effective HEMTs for power switching applications.

Monolithic Si-Based AlGaN/GaN MIS-HEMTs Comparator and Its High Temperature Characteristics

Monolithic GaN High Electron Mobility Transistor (HEMT)-integrated circuits are a promising application of wide band-gap materials. To date, most GaN-based devices behave as NMOS-like transistors. As only NMOS GaN HEMT is currently commercially available, its control circuit requires special design if monolithic integration is desired. This article analyzes the schematics of a GaN-based comparator, and three comparator structures are compared through ADS simulation. The optimal structure with the bootstrapped technique is fabricated based on AlGaN/GaN Metal–Insulator–Semiconductor (MIS) HEMT with the recessed gate method. The comparator has excellent static characteristics when the reference voltage increases from 3 V to 8 V. Dynamic waveforms from 10 kHz to 1 MHz are also obtained. High-temperature tests from 25 °C to 250 °C are applied upon both DC and AC characteristics. The mechanisms of instability issues are explained under dynamic working condition. The results prove that the comparator can be used in the state-of-art mixed-signal circuits, demonstrating the potential for the monolithic all-GaN integrated circuits.

Understanding the Thermal Time Constants of GaN HEMTs through Model Order Reduction Technique

This paper described a comparison between a numerical Finite Element Analysis (FEA) and an analytical approach in order to extract the thermal time constants and the thermal resistances of simple but realistic structures. Understanding the complex contribution of multidimensional thermal spreading, the effect of multiple layers, and the correlation with the heat source length is mandatory due to the severe mismatch of thermal expansion in different epitaxial layers and high operating temperatures. This is especially true on GaN HEMT (High Electron Mobility Transistor) with the continuous decrease of the gate length and the increase of the power density. Moreover, in this paper, we extracted the time constants with a Model Order Reduction (MOR) technique based on the Ritz vector approach with inputs coming from the FE matrices. It was found that the time constants obtained by an analytical solution and a model order extraction from FEA were exactly the same. This result validated the idea that our MOR technique provides the real time constants and resistances for our device structures and in this case unified the analytical world with the numerical one.

Quantitative analysis of electrically active defects in Au/AlGaN/GaN HEMTs structure using capacitance–frequency and DLTS measurements

Electrical trap states in the AlGaN-based high-electron-mobility transistor (HEMT) structures limit the performances of devices. In this study, we present a comprehensive study of the electrical trap states in AlGaN/GaN HEMT structures and examine their influence on the device performance. We performed capacitance–frequency and conductance–frequency measurements to determine the time constant and the density of the interface states. The density of the interface states was calculated to be 2 × 1010 cm−2 eV−1, and the time constant of the interface states was 1 μs. Deep-level transient spectroscopy showed the presence of one electron trap E1 (negative peak) and three hole-like traps P1, P2, and P3 (positive peaks). The thermal activation energies for E1, P1, P2, and P3 traps were calculated to be 1.19, 0.64, 0.95, and 1.32 eV, respectively. The electron trap E1 and the hole-like traps P1, P2 and P3 were observed to originate from the point defects or their complexes in the material. The hole-like traps reflected the changes created in the population of the surface states owing to the capture of the surface states; these traps originated from the point defects related to the nitrogen vacancy.

Defect characterization of heavy-ion irradiated AlInN/GaN on Si high-electron-mobility transistors

The characteristic energies of traps in InAlN/AlN/GaN high-electron mobility transistor structures on Si(111) substrates formed after irradiation with 75 MeV S-ions is studied by means of c-lattice parameter analysis, vertical IV-characteristics, micro-photoluminescence (µ-PL), photocurrent (PC) and thermally stimulated current (TSC) spectroscopy. From the lattice parameter analysis, point defect formation is concluded as the dominant source of defects upon irradiation. A strong compensation effect mani-fests itself through enhanced resistivity of the devices as found in vertical IV- measure-ments. The defect formation is detected optically by an additional PL-band within the green spectral region while defect states with threshold energies at 2.9 eV and 2.65 eV were observed by PC spectroscopy. TSC spectra exhibit two defect-related emissions between 300 K and 400 K with thermal activation energies of 0.78-0.82 eV and 0.91-0.98 eV, respectively. The data further supports the formation of Ga vacancies (VGa) and related complexes acting mainly as acceptors compensating the originally undoped n-type GaN buffer layers after irradiation.