The field of high-frequency device research requires the utilization of a vector network analyser and the advanced calibration methods to correct measurement imperfections caused by two RF signal paths, from the signal generator/detector to the probe tips and probe tips to the on-chip device under test (DUT). Plenty of the calibration methods utilizing reference RF devices including robust calculations were already introduced. This paper deals with imperfection correction of the probe tips to the on-chip DUT RF signal path. OPEN, SHORT, THRU on-chip test structures are used together with iteration calculations which allow for a simple implementation into automated calibration process. Vector error correction of s- parameters obtained by calibration process are subsequently employed in de- embedding process to acquire s-parameters of a DUT.

This study presents a thermo-mechanical simulation of a power SiC transistor integrated into a printed circuit board (PCB). The primary objective is to optimize the design to enhance the thermal and mechanical properties of the device. Through numerical simulations, critical areas within systems utilizing power transistors embedded in PCBs are identified and optimized to reduce mechanical strain and improve heat dissipation. These improvements contribute to the overall reliability of the final system.

High-frequency wireless communication in consumer, defense, and space applications heavily relies on the use of compound semiconductor amplifiers. Typically, the X to Ka wireless bands (similar to 8-40 GHz) are covered by GaN and GaAs-based devices, respectively, to the desired output power. GaAs-based high-electron mobility transistors (HEMTs) provide an unprecedented ultralow-noise high-frequency operation even at cryogenic temperatures, critically important for the high-fidelity amplification of weak qubit states in quantum computing. Increased output power from GaAs-based devices while maintaining low self-heating is an important but challenging objective. In this study, we used an epitaxial lift-off (ELO) technique to transfer GaAs nanomembranes onto foreign substrates (sapphire, Si, and SiC) and analyzed the thermal properties of the van der Waals-bonded GaAs films by nanosecond transient thermoreflectance (TTR). Electrothermal simulation of a GaAs HEMT was used to predict the thermal performance of the transferred devices, and a significant decrease of similar to 30% in the device thermal resistance (Rth) was observed when SiC and diamond substrates were used. Our results also predict that the on-state channel temperature rise can be further decreased by similar to 29 to 41% if the GaAs/substrate interface is improved by increased thermal boundary conductance. Our study finds that the ELO-transferred GaAs HEMTs onto foreign highly thermally conductive substrates can significantly improve their thermal performance and allow for higher output while keeping the on-state temperature within the safe operating margin.

In this article, pinch-off voltage biasing was utilized for the first time to determine the average channel temperature of the AlGaN/GaN HEMT, which made it possible to exclude the device’s electrical parameters dependence in the linear operating mode. The theoretical part is focused on the thermal model with temperature-dependent thermal resistance utilization for active area average temperature determination of the HEMT under quasi-static operation. The experimental part deals with drain-to-source current comparison utilizing quasi-static and pinch-off voltage-biased short-pulse output ${I}$ – ${V}$ characteristics and additional isothermal trapping phenomena determined from the threshold voltage shift. The appropriate use and combination of methods for the active area average temperature determination utilizing constant isothermal saturation current or short-pulse current were discussed.

The modified thermal device model was adapted to determine the channel temperature of the AlGaN/GaN HEMT operating under pulsed and quasi-static conditions. The differential analysis of the isothermal and thermal part of the resulting current, as well as ambient temperature variation, is utilized to determine the average channel temperature. Ambient temperature increases in the device operating range is required under low-power operation only, while under high-power operation the thermal stress of the device is significantly reduced due to small ambient temperature variation. In addition, trapping phenomena incorporation is demonstrated to obtain more accurate results utilizing the HEMT threshold voltage shift and transconductance. For experimental verification of the thermal model, Al0.25Ga0.75N/GaN HEMT electrical properties are investigated. Experimentally verified results are in a good agreement with numerical simulations.

Basic knowledge about the factors and mechanisms affecting the performance of solar cells and their identification is essential when thinking of future improvements to the device. Within this paper, we investigated the current transport mechanism in GaAsN p-i-n solar cells grown with atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE). We examined the electro-optical and structural properties of a GaAsN solar cell epitaxial structure and correlated the results with temperature-dependent current-voltage measurements and deep level transient spectroscopy findings. The analysis of J-V-T measurements carried out in a wide temperature range allows for the determination of the dominant current transport mechanism in a GaAsN-based solar cell device and assign it a nitrogen interstitial defect, the presence of which was confirmed by DLTFS investigation.

A differential analysis of electrical attributes, including the temperature profile and trapping phenomena is introduced using a device analytical spatial electrical model. The resultant current difference caused by the applied voltage variation is divided into isothermal and thermal sections, corresponding to the instantaneous time- or temperature-dependent change. The average temperature relevance is explained in the theoretical section with respect to the thermal profile and major parameters of the device at the operating point. An ambient temperature variation method has been used to determine device average temperature under quasi-static state and pulse operation, was compared with respect to the threshold voltage shift of a high-electron-mobility transistor (HEMT). The experimental sections presents theoretical subtractions of average channel temperature determination including trapping phenomena adapted for the AlGaN/GaN HEMT. The theoretical results found using the analytical model, allow for the consolidation of specific methodologies for further research to determine the device temperature based on spatially distributed and averaged parameters.

We propose a novel model approach for temperature evaluation in the channel region of a InAlN/AlN/gallium nitride high electron mobility transistor (HEMT) due to self-heating effects. The heat transfer in a HEMT device has been investigated experimentally by the nearby temperature sensor and compared by theoretical models solved by both numerical and analytical methods. The average temperature of the channel area of almost 160 °C for dissipated power of 2 W was determined using the drain-source current variation analysis. The electrical and thermal behavioral numerical model under quasi-static conditions have been used to describe the HEMT device. In contrast, the one-dimensional thermal model for analytical evaluation has been proposed as an alternative approach. Surprisingly, the experimental results verified not only the validity of precise numerical simulation but also the simplified analytical model that makes it a reliable tool even for complex electronic devices.

This work deals with the average temperature model of two AlGaN/GaN HEMTs exhibiting similar thermal but different electrical properties. Output I-V characteristics dependent on isothermal and thermal device properties allow comparison of output conductance and current temperature sensitivity of both devices. Nevertheless thermal gradient and dissipated power density variation in the active device area give the model some restrictions. However more input thermal parameters bring availability to perform more accurate calculations.

In this paper, several methods suitable for real time on-chip temperature measurements of power AlGaN/GaN-based high-electron mobility transistor (HEMT) grown on a SiC substrate are presented. The measurement of temperature distribution on HEMT surface using Raman spectroscopy is presented. The second approach utilizes electrical I-V characteristics of the Schottky diode neighboring to the heat source of the active transistor under different dissipated power for temperature measurement. These methods are further verified by measurements with microthermistors. The features and limitations of the proposed methods are discussed. The thermal parameters of materials used in the device are extracted from the temperature distribution in the structure with the support of three-dimensional thermal simulation of the device. Thermal analysis of the multifinger power HEMT is performed. The effects of the structure design and fabrication processes from semiconductor layers, metallization, and packaging up to cooling solutions are investigated. The influence of individual layer properties on the thermal performance of different HEMT structures under different operating conditions is presented. The results show that the proposed experimental methods supported by simulation have a potential for the design, analysis, and thermal management of HEMT.

An improved method of average channel temperature and channel temperature profile determination is introduced in this paper applied to AlGaN/GaN HEMT using quasi-static I–V characterization and external heater. Particular HEMT resistances and threshold voltage were experimentally determined at different ambient temperatures from TLM measurements, HEMT output and transfer I–V characteristics. Negligible pinch-off area and leakage current dependence on drain voltage allows to obtain average temperature ∼77 °C for dissipated power 1.5 W using simple recurrent differential calculations. The HEMT channel temperature profile exhibiting maximum peripheral temperature ∼130 °C for dissipated power 1.5 W was simulated and verified utilizing the device electrical parameters variation.

This paper proposes a novel method of average channel temperature and channel temperature profile determination is discussed in theoretical part and subsequently applied to InAlN/AlN/GaN HEMT using quasi-static I–V characterization supported by thermal 3D FEM simulations. Experimentally was determined HEMT source resistance and threshold voltage from low-power output and transfer I–V characteristics at different thermal chuck temperatures. The HEMT channel average temperature nearly 88 °C for dissipated power 2 W was calculated taking advantage of the drain current change analysis applied in recurrent differential form. Additionally, the HEMT channel temperature profile was simulated utilizing the calculated channel dissipated power density.

GaN-based HEMTs' high potential is deteriorated by self-heating during the operation, this has influence on the electrical properties as well as device reliability. This work is focused on an average channel temperature determination of power AlGaN/GaN HEMT prepared on SiC substrate using quasi-static and pulsed I-V characterization. There was analyzed the drain current change relation to temperature dependent electrical HEMT parameters such as source resistance, threshold voltage, saturation velocity, resp. leakage current which allows to calculate an average channel temperature versus dissipated power for various ambient temperature. Differential temperature of investigated device with and without heatsink was determined. Obtained results were discussed using simulated spatial temperature distribution.

In this paper, several methods suitable for real time on-chip temperature measurements of power AlGaN/GaN based high-electron mobility transistor (HEMT) grown on SiC substrate are presented. The measurement of temperature distribution on HEMT surface using Raman spectroscopy is presented. We have deployed a temperature measurement approach utilizing electrical I-V characteristics of the neighboring Schottky diode under different dissipated power of the transistor heat source. These methods are verified by measurements with micro thermistors. The results show that these methods have a potential for HEMT analysis in thermal management. The features and limitations of the proposed methods are discussed. The thermal parameters of materials used in the device are extracted from temperature distribution in the structure with the support of 3-D device thermal simulation. The thermal analysis of the multifinger power HEMT is performed. The effects of the structure design and fabrication processes from semiconductor layers, metallization, and packaging up to cooling solutions are investigated. The analysis of thermal behavior can help during design and optimization of power HEMT.

In this work an average channel temperature of power InAIN/GaN HEMT prepared on SiC substrate has been investigated using quasi-static 1-V characterization. The analysis of drain current change depending on source resistance, threshold voltage and saturation velocity drop was utilized and used for temperature versus dissipated power calculations in differential form. The source resistance and threshold voltage were determined experimentally by measurements of output and transfer characteristics at different ambient temperatures whereas saturation velocity relative drop was used from available resources. Obtained results were compared with simulations.

Temperature-induced instability of the threshold voltage in GaN-based heterostructure field-effect transistors (HFETs) and Al2O3-and ZrO2-based metal-oxide-semiconductor (MOS) HFETs was investigated and their trapping effects were analyzed. A negative or positive threshold voltage shift was observed in the HFETs with a AlGaN or InAlN barrier, which indicates that electron or hole traps dominate in the barriers. A temperature dependence of the threshold voltage in the MOSHFETs exhibited two different regions. At lower temperatures, similarly as in the HFETs, traps in the barrier dominated. However, at temperatures above 100 -150 degrees C the threshold voltage shift was more pronounced and connected with the oxide/insulator interface traps. The threshold voltage shift can be negative or positive if a Al2O3 or ZrO2 gate insulator, respectively, is used. The results show that the temperature dependence of the threshold voltage can be controlled by the barrier layer composition and/or the gate insulator type.

The present work reports the fabrication of p-Si/SiO2/TiO2 and p-Si/SiO2/TiO2/ZnO heterostructures deposited by RF sputtering on p-Si substrate. The structural properties of the heterostructures were characterized by X-ray reflectivity and SIMS depth profiling. The electrical and optical properties of the heterostructures were investigated by I-V, C-V measurements and VIS spectroscopy, respectively. The measurements reveal that I-V characteristics in dark show semiconductor-insulator-semiconductor (SIS) structure properties. The I-V characteristics under illumination exhibit changes with significant increase of photocurrent due to photoassisted tunnelling and injection through SiO2/TiO2 interlayer.

This work deals with the trap analysis of the GaN-based structures using current time response on the voltage pulse applied to Schottky and ohmic contacts containing AlGaN and InAlN layers with different composition and thickness. Monitoring of the current time evolution for the investigated samples allows identifying and comparing particular traps. The analysis of the current transients measured at various temperatures via fitting up to four exponentials is used to resolve traps located in the particular layers and their activation energies were determined.

Trapping effects on two AlGaN/GaN Schottky diodes with a different composition of the AlGaN barrier layer were analyzed by current transient spectroscopy. The current transients were measured at a constant bias and at six different temperatures between 25 and 150 °C. Obtained data were fitted by only three superimposed exponentials, and good agreement between the experimental and fitted data was achieved. The activation energy of dominant traps in the investigated structures was found to be within 0.77–0.83 eV. This nearly identical activation energy was obtained from current transients measured at a reverse bias of −6 V as well as at a forward bias of+1 V. It indicates that the dominant traps might be attributed to defects mainly associated with dislocations connected predominantly with the GaN buffer near the AlGaN/GaN interface.