Steady State and Transient Thermal Characterization of Vertical GaN PIN Diodes

2017 ◽  
Author(s):  
Georges Pavlidis ◽  
James Dallas ◽  
Sukwon Choi ◽  
Shyh-Chiang Shen ◽  
Samuel Graham
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Sapphire Substrate ◽  
Temperature Rise ◽  
Thermal Response ◽  
Thermal Characterization ◽  
Peak Temperature ◽  
Accurate Estimation ◽  
Pin Diode ◽  
Pin Diodes

In this work, we investigate the thermal response of GaN PIN diodes grown on a sapphire substrate and compare the results to GaN PIN diodes grown on a free standing GaN substrate (FS-GaN). Until now, thermal characterization techniques have been developed to assess the temperature distribution across lateral devices. Raman thermometry has shown to accurately measure the temperature rise across the depth of the GaN layer. Implementing this technique to assess the temperature distribution across the depth of a vertical GaN device is more challenging since a volumetric depth average is measured. The use of TiO2 nanoparticles is shown to overcome this issue and reduce the uncertainty in the peak temperature by probing a surface temperature on top of the device. For the sapphire substrate, an additional temperature rise of about 15 K was seen on the surface of the PIN diode as compared to the average in the bulk. While the steady state thermal measurements show an accurate estimation of the device’s peak temperature, the PIN diodes are normally operated under pulsed conditions and the thermal response of these devices under periodic joule heating must be assessed. A recently developed transient thermoreflectance imaging technique (TTI) is used in this study to monitor transient temperature rise and decay of top metal contact. Under the same biasing conditions, the FS-GaN PIN diode is found to result in less than half the temperature rise obtained by the sapphire substrate diode. Extracting time constants, a longer rise and decay is also observed in the sapphire substrate diode.

scholarly journals Post Fire Transient Temperature Distribution in Drum Type Packages

2006 ◽  
Author(s):  
Allen C. Smith
Keyword(s):  
Temperature Distribution ◽  
Thermal Resistance ◽  
Heat Generation ◽  
Thermal Response ◽  
Internal Resistance ◽  
Peak Temperature ◽  
Transient Temperature ◽  
Containment Vessel ◽  
Transient Temperature Distribution ◽  
Parametric Studies

This study investigates the temperature distribution in an idealized cylindrical package subjected to the HAC Fire transient. Cases for several common overpack materials, with thermal conductivity spanning two orders of magnitude, are considered. The results show that the interior temperature distribution and maximum interior temperature are determined by the heat generation of the contents and the thermal resistance of the package materials. Heat generation has a dominant effect on the peak temperature in the center (containment vessel region) of the package, when the internal thermal resistance is high. For cases where the internal resistance is low, heat conducted into the interior during the fire determines the peak temperature in the center, containment vessel region. The thermal wave effect, where the interior temperature continues to rise after the end of the fire exposure, is present in all cases. The study complements the parametric studies of effects of thermal properties on thermal response of packages which were previously reported.

Thermal analysis, design, and characterization of a reconfigurable switch matrix based on LTCC technology for satellite communications

2014 ◽  
Vol 2014 (1) ◽  
pp. 000692-000697
Author(s):  
S. Kaleem ◽  
S. Rentsch ◽  
T. Welker ◽  
J. Müller ◽  
M.A. Hein
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Thermal Resistance ◽  
Simulation Model ◽  
Integrated Circuit ◽  
Thermal Characteristics ◽  
Cumulative Effect ◽  
Satellite Communications ◽  
Peak Temperature ◽  
Current Limiting

The thermal characteristics of a reconfigurable switch matrix (RSM) module based on low temperature co-fired ceramic (LTCC) technology are presented. Owing to the PIN-diodes based design, a static power of 1.6 W is dissipated on the ceramic package; the double-sided mounting and integrated bias circuitry demands determination of the temperature distribution within the module. A finite-element thermal simulation model was validated by an infrared (IR) thermograph; the steady-state temperature distribution on the surface of the package estimated by the simulation model differs to the IR measurements by < 1%. This temperature distribution is the result of the thermal interaction among components on the multi-die package with different electrical power dissipation. The temperature on the multi-throw switch monolithic microwave integrated circuit (MMIC) is elevated by ~36.7 K relative to the ambient temperature. The peak temperature occurs on the current-limiting resistors in the bias circuitry; the peak temperature is estimated to be ~45 K above the ambient. In a later version of the RSM, the bias current was reduced by 50%, current-limiting resistor was replaced by two parallel resistors, and additional thermal vias and conductive pads were introduced on the ceramic package. The cumulative effect is a temperature distribution on the package with lowered values. Compared to its predecessor, the temperatures at the current-limiting resistor and the MMIC are reduced by ~20 K and ~14 K, respectively. With one heat source active on the ceramic package at a time, the resulting steady-state temperatures on this source and the remaining heat sources provided an estimate of the self- and transfer-thermal resistances, respectively. The reciprocity of the heat flow on the package and the three-dimensional symmetric layout required only ‘4’ thermal simulations to determine the symmetric thermal resistance matrix. The significantly reduced values of the computed matrix for the later version of the RSM module demonstrated lower thermal resistance to the ambient, compared to its predecessor. Lastly, the results of thermal measurements conducted with a vacuum wafer prober are presented, in order to validate RSM functionality for vacuum pressures (≤ 1 mPa) and temperatures between 248 K and 338 K; the control current and the transmission coefficient demonstrated variations of ≤ 0.5% and −0.015 dB/K, respectively.

Virtual Thermal Sensing and Control of Heat Distribution Using State Estimation

2012 ◽  
Author(s):  
Kaveh Fathian ◽  
Fatemeh Hassanipour ◽  
Nicholas R. Gans
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Heat Flow ◽  
Control Method ◽  
Industrial Applications ◽  
Electrical Circuit ◽  
Accurate Estimation ◽  
Plate Temperature ◽  
And Control ◽  
State Error

Many industrial applications require or can be improved by strict control of the temperature distribution on a surface. This initial investigation presents modeling and control of heat flow on an aluminum plate. Temperature distribution is modeled using a dense equivalent electrical circuit. An observer is designed based on the model to estimate the temperature distribution on the plate. The estimation is used in a controller to regulate the temperature of a desired point on the plate, given discrete heat input elements but no cooling elements. Experiments are conducted to compare the realism of the heat flow model and efficacy of the control method with experimental data. Results show that the steady state error between the actual and estimated temperatures at different points on the surface is always less than 0.5°C, which indicates accurate estimation of the temperature. The RMS error between desired and actual temperatures through all experiments is less than 2°C which indicates fast regulation and low steady state error.

Steady-state heat sink analysis for two-terminal microwave oscillator devices with temperature dependent thermal conductivity

1993 ◽  
Vol 441 (1911) ◽  
pp. 181-189 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Steady State ◽  
Temperature Distribution ◽  
Temperature Rise ◽  
Heat Sink ◽  
Maximum Temperature ◽  
Microwave Oscillators ◽  
Steady State Temperature ◽  
Steady State Heat

A theoretical analysis to calculate the steady-state temperature distribution within a cylindrical heat sink configuration, where the thermal conductivity is dependent on the temperature, is outlined. The analysis applies to any heat sink arrangement that can be treated as one or more homogeneous solid cylinders mounted on a semi-infinite heat sink, where the heat flux incident on both faces of each cylinder is uniform over a given centralized circular region. The model is used to analyse the temperature distribution within the heat sink configurations used commonly to package two-terminal semiconductor devices that are operated as sources of electromagnetic radiation in microwave oscillators. Results are presented that show how the maximum temperature rise within commercially available heat sink packages, depends on the input heat flux and the dimensions and thermal conductivity of the materials. Furthermore, results that show how the temperature rise varies across the interfaces of given heat sink configurations, similar to those used commercially, are given also.

High-speed isotachophoresis. Analytical aspects of the steady-state longitudinal temperature profiles

1979 ◽  
Vol 44 (3) ◽  
pp. 841-853 ◽  
Author(s):  
Zbyněk Ryšlavý ◽  
Petr Boček ◽  
Miroslav Deml ◽  
Jaroslav Janák
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Minor Component ◽  
Physical Models ◽  
Temperature Profiles ◽  
Longitudinal Temperature ◽  
Continuous Character

The problem of the longitudinal temperature distribution was solved and the bearing of the temperature profiles on the qualitative characteristics of the zones and on the interpretation of the record of the separation obtained from a universal detector was considered. Two approximative physical models were applied to the solution: in the first model, the temperature dependences of the mobilities are taken into account, the continuous character of the electric field intensity at the boundary being neglected; in the other model, the continuous character of the electric field intensity is allowed for. From a comparison of the two models it follows that in practice, the variations of the mobilities with the temperature are the principal factor affecting the shape of the temperature profiles, the assumption of a discontinuous jump of the electric field intensity at the boundary being a good approximation to the reality. It was deduced theoretically and verified experimentally that the longitudinal profiles can appreciably affect the longitudinal variation of the effective mobilities in the zone, with an infavourable influence upon the qualitative interpretation of the record. Pronounced effects can appear during the analyses of the minor components, where in the corresponding short zone a temperature distribution occurs due to the influence of the temperatures of the neighbouring zones such that the temperature in the zone of interest in fact does not attain a constant value in axial direction. The minor component does not possess the steady-state mobility throughout the zone, which makes the identification of the zone rather difficult.

scholarly journals C-Band and X-Band Switchable Frequency-Selective Surface

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 476
Author(s):  
Umer Farooq ◽  
Adnan Iftikhar ◽  
Muhammad Farhan Shafique ◽  
Muhammad Saeed Khan ◽  
Adnan Fida ◽  
...  
Keyword(s):  
Bottom Layer ◽  
Frequency Selective Surface ◽  
Transverse Magnetic ◽  
Unit Element ◽  
Angular Stability ◽  
Band Spectrum ◽  
Pin Diode ◽  
Pin Diodes ◽  
X Band ◽  
Frequency Selective

This paper presents a highly compact frequency-selective surface (FSS) that has the potential to switch between the X-band (8 GHz–12 GHz) and C-band (4 GHz–8 GHz) for RF shielding applications. The proposed FSS is composed of a square conducting loop with inward-extended arms loaded with curved extensions. The symmetric geometry allows the RF shield to perform equally for transverse electric (TE), transverse magnetic (TM), and 45° polarizations. The unit cell has a dimension of 0.176 λ0 and has excellent angular stability up to 60°. The resonance mechanism was investigated using equivalent circuit models of the shield. The design of the unit element allowed incorporation of PIN diodes between adjacent elements for switching to a lower C-band spectrum at 6.6 GHz. The biasing network is on the bottom layer of the substrate to avoid effects on the shielding performance. A PIN diode configuration for the switching operation was also proposed. In simulations, the PIN diode model was incorporated to observe the switchable operation. Two prototypes were fabricated, and the switchable operation was demonstrated by etching copper strips on one fabricated prototype between adjacent unit cells (in lieu of PIN diodes) as a proof of the design prototypes. Comparisons among the results confirmed that the design offers high angular stability and excellent performance in both bands.

scholarly journals Investigation on the Non-Uniform Temperature Distribution of Large-Diameter Concrete Silos under Solar Radiation

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Liang Zhao ◽  
Zhiyong Yang ◽  
Lijie Wang
Keyword(s):  
Temperature Field ◽  
Steady State ◽  
Temperature Distribution ◽  
Temperature Effects ◽  
Large Diameter ◽  
Fe Model ◽  
Concrete Walls ◽  
Steady State Method ◽  
Nonlinear Temperature ◽  
Internal Forces

There is a growing demand for silos with large diameters and volumes; hence, the stresses induced by the temperature differences between the inner and the outer surfaces of the concrete walls of the large silos become significant. Sunshine is the main source of the temperature differences; and it is necessary to investigate the influences of sunshine on large concrete silos and ensure their safety and durability. In this paper, the temperature distribution of a concrete silo exposed to the sunshine was measured on site. A finite element (FE) model was built to analyze the temperature distribution under the sunshine, and the FE model was validated by comparing the yielded temperature field with that obtained on site. Based on the temperature field yielded in the FE model, the internal forces of the silo were determined by performing a structural analysis. After that, the FE model was extended and used for a parametrical study, and the influences induced by the factors like meteorological parameters, dimension of silos, and reference temperature on the temperature effects of the silo were investigated. The simulation results showed that the temperature gradient exhibited significant nonlinearities along the wall thickness. The performance of a steady-state analytical method was evaluated, which is conventionally used for the design of silos. It was found that, for the silos with the thicknesses of more than 30 centimeters, the steady-state method overestimated the temperature effects. It is suggested here that nonlinear temperature gradients should be employed for considering the temperature effects of large silos.

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