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Journal ArticleDOI

Channel Temperature Analysis of GaN HEMTs With Nonlinear Thermal Conductivity

TL;DR: In this article, an enhanced, closed-form expression for the thermal resistance, and thus, the channel temperature of AlGaN/gallium nitride (GaN) HEMTs, including the effect of the temperature-dependent thermal conductivity of GaN and SiC or Si substrates, is presented.
Abstract: This paper presents an enhanced, closed-form expression for the thermal resistance, and thus, the channel temperature of AlGaN/gallium nitride (GaN) HEMTs, including the effect of the temperature-dependent thermal conductivity of GaN and SiC or Si substrates. In addition, the expression accounts for temperature increase across the die-attach. The model’s validity is verified by comparing it with experimental observations. The model results also compare favorably with those from finite-element numerical simulations across the various device geometric and material parameters. The model provides a more accurate channel temperature than that from a constant thermal conductivity assumption; this is particularly significant for GaN/Si HEMTs where the temperature rise is higher than in GaN/SiC. The model is especially useful for device and monolithic microwave integrated circuit designers in the thermal assessment of their device design iterations against required performance for their specific applications.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a scalable electrothermal large-signal AlGaN/GaN HEMTs model for both fundamental and multiharmonics is presented based on the modified Angelov model.
Abstract: A scalable electrothermal large-signal AlGaN/GaN HEMTs model for both fundamental and multiharmonics is presented based on the modified Angelov model. To obtain accurate scalability of the electrothermal model, a simple empirical expression is proposed for the geometric and power-dissipation-dependent nonlinear thermal resistance $R_{{\mathrm {th}}}$ . Only one additional parameter with linear scaling rule is needed in the drain-source current ( $I_{{\mathrm {ds}}}$ ) model for a scalable large-signal multiharmonic model. The proposed model has been validated by different AlGaN/GaN HEMTs characterized by on-wafer measurements. It shows that the presented scalable model can well predict the dc $I$ – $V$ , pulsed $I$ – $V$ , scattering (S) parameters, and large-signal performance up to third harmonic. Furthermore, to further validation, a C-band power amplifier is designed. The amplifier is realized using the second-harmonic tuned approach to enhance the efficiency. Measurement results show that the GaN high power amplifier (HPA) microwave monolithic integrated circuit (MMIC) exhibits more than 40% power-added efficiency and 60-W output power ( $P_{{\mathrm {out}}}$ ) with associated gain of 25 dB in 5–6 GHz measured at 28-V drain voltage and pulse signal with 100- $\mu \text{s}$ pulsewidth and 10% duty cycle. The area of the chip is 3.2 mm $\times5.3$ mm (16.96 mm2). These results show that the proposed model will be useful for high-efficiency HPA MMIC design.

79 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used coupled electron and phonon Monte Carlo (MC) simulations to provide the most accurate temperature predictions of the transistor region, where the phonon MC simulations can be coupled with conventional Fourier's law analysis for regions away from the transistor.

41 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the phonon Monte Carlo (MC) method to investigate the thermal spreading resistance in a ballistic-diffusive regime for gallium-nitride (GaN) high-electron-mobility transistors.
Abstract: To develop an efficient thermal design for gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) that usually hold a super-high-power density, it is essential to accurately predict the junction temperature. In GaN HEMTs, the heat transfer process is dominated by thermal spreading resistance. Moreover, the phonon mean free paths (MFPs) of GaN are comparable with the channel layer thickness and the heat spot width. Thus, a ballistic effect emerges, resulting in the invalidity of Fourier’s heat conduction law. Therefore, Fourier’s law-based thermal resistance model should be reexamined and modified for this case. In this paper, we used the phonon Monte Carlo (MC) method to investigate the thermal spreading resistance in a ballistic-diffusive regime for GaN HEMTs. Our simulation results indicate that the ballistic effect significantly altered the temperature distributions within channel layers and resulted in a dramatic increase in the thermal resistance when compared with Fourier’s law-based predictions. Furthermore, a semiempirical thermal resistance model with a fitting parameter was derived. This model can accurately address the issues of thermal spreading and the ballistic effect. This paper can provide a more in-depth understanding of the thermal spreading resistance in a ballistic-diffusive regime, and it can be useful for the prediction of junction temperatures and for the thermal management of HEMTs.

41 citations


Cites background from "Channel Temperature Analysis of GaN..."

  • ...[5] developed an HEMT thermal resistance model in a more practical case and improved the model by considering the temperature dependence of thermal conductivity [14]....

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Journal ArticleDOI
TL;DR: In this paper, the authors studied the self-heating mechanism and its impact on electrical performance of short gate length GaN high electron mobility transistors (HEMTs) based on electrothermal TCAD simulations.
Abstract: In this paper, we study the self-heating mechanism and its impact on electrical performance of short gate length GaN high electron mobility transistors (HEMTs) based on electrothermal TCAD simulations. We propose an equivalent channel temperature to quantify the current degradation due to self-heating and also resolve the discrepancies between temperature measurements through electrical methods and thermal methods in the literature. We then explain the equivalent channel temperature’s behavior using the temperature- and field-dependent electron transport theory for short gate length HEMTs. The implications and guidelines to the various aspects of device design are also discussed.

39 citations


Cites background or methods from "Channel Temperature Analysis of GaN..."

  • ..., the heat source is assumed the same as the gated channel in some FEA simulations [10], [12] and analytical derivations [15], [16]; whereas in [11] it is found that a heat source with twice the gate length and centered around the drain-side gate edge can fit best with measured thermal resistance....

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  • ...self-heating effect in GaN HEMTs relies on locating the heat source in the channel and then solving the heat flow equation, either through finite element analysis (FEA) [10]–[14] or analytical solutions [14]–[16]....

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Journal ArticleDOI
TL;DR: The proposed method is based on decomposing the device nonlinearity into intrinsic trapping-induced and thermal-induced nonlinearities that can be simulated by low-order ANN models to simulate the transistor.
Abstract: This paper presents an efficient artificial neural network (ANN) electrothermal modeling approach applied to GaN devices. The proposed method is based on decomposing the device nonlinearity into intrinsic trapping-induced and thermal-induced nonlinearities that can be simulated by low-order ANN models. The ANN models are then interconnected in the physics-relevant equivalent circuit to accurately simulate the transistor. Genetic algorithm (GA)-based training procedure has been implemented to find optimal values for the weights of the ANN models. The modeling approach is used to develop a large-signal model for a 1-mm gate-width GaN high-electron mobility transistor (HMET). The model has been implemented in the advanced design system (ADS) and it has been validated by pulsed and continues small- and large-signal measurements. The model simulations showed a very good agreement with the measurements and verify the validity of the developed technique for dynamic electrothermal modeling of active devices.

37 citations


Cites methods from "Channel Temperature Analysis of GaN..."

  • ...The complete drain current can be expressed as: Ids = Ids,iso(Vgs,Vds,T )+ Ids,diff (Vgs,Vds,Vgso,Vdso) (6) where Ids,iso is determined by (1) and T is calculated using (3)-(5) and it depends on the ambient temperature in addition to the power dissipation Pdiss....

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  • ...The dependence of Rth on Pdiss [28] has been considered by implementing the following formula: Rth = [1+ 2(1+ 0.1× tanh(Pdiss − 9))Pdiss]Pdiss....

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  • ...In general, the drain current can be represented by the same model in (1) but the temperature T could be extended to consider also the self-heating as follows: T = RthPdiss + (Tref +1T ) (3) where 1T is the rise of ambient temperature with respect to reference ambient temperature Tref (typically at around 25 ◦C) and Pdiss is the intrinsic power dissipation (Pdiss = VdsIds)....

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  • ...6(b) shows the measured and simulated Pdiss with meansquare-error of 7.2×10−2....

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  • ...Pdiss in (3) is predicted by its ANN model and its static/quasi-static values are extracted by a low pass circuit....

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References
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Book
01 Jan 1972
TL;DR: In this paper, the authors present a list of superconductivity properties of solids with respect to periodic structure, lattice wave properties, electron states, and electron-electron interaction.
Abstract: 1. Periodic structure 2. Lattice waves 3. Electron states 4. Static properties of solids 5. Electron-electron interaction 6. Dynamics of electrons 7. Transport properties 8. Optical properties 9. The fermi surface 10. Magnetism 11. Superconductivity Bibliography Index.

1,892 citations

Journal ArticleDOI
Glen A. Slack1
TL;DR: The diamond has the highest known thermal conductivity at 300k K at room temperature as discussed by the authors, and is the only non-metallic crystal with thermal conductivities of > 1 W/cmK at 300K.

1,523 citations

Journal ArticleDOI
16 Jan 2008
TL;DR: The latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, are reviewed to achieve the state-of-the-art microwave and millimeter-wave performance.
Abstract: The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage and high input impedance GaN-based RF power devices have made substantial progresses in the last decade This paper attempts to review the latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, to achieve the state-of-the-art microwave and millimeter-wave performance The reliability and manufacturing challenges are also discussed

1,503 citations


"Channel Temperature Analysis of GaN..." refers background in this paper

  • ...In nominal, thermally limited device characterizations, it is typical to predict excellent power densities for large devices based on small device measurements [1]–[3], with low self-heating, and then observe a significant reduction [4]...

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Journal ArticleDOI
TL;DR: In this article, a GaN high-electron-mobility-transistors (HEMTs) on SiC were fabricated with field plates of various dimensions for optimum performance, and an enhancement in radio frequency (RF) current-voltage swings was achieved with acceptable compromise in gain, through both reduction in the trapping effect and increase in breakdown voltages.
Abstract: GaN high-electron-mobility-transistors (HEMTs) on SiC were fabricated with field plates of various dimensions for optimum performance Great enhancement in radio frequency (RF) current-voltage swings was achieved with acceptable compromise in gain, through both reduction in the trapping effect and increase in breakdown voltages When biased at 120 V, a continuous wave output power density of 322 W/mm and power-added efficiency (PAE) of 548% at 4 GHz were obtained using devices with dimensions of 055/spl times/246 /spl mu/m/sup 2/ and a field-plate length of 11 /spl mu/m Devices with a shorter field plate of 09 /spl mu/m also generated 306 W/mm with 496% PAE at 8 GHz Such ultrahigh power densities are a dramatic improvement over the 10-12 W/mm values attained by conventional gate GaN-based HEMTs

1,077 citations


"Channel Temperature Analysis of GaN..." refers background in this paper

  • ...In nominal, thermally limited device characterizations, it is typical to predict excellent power densities for large devices based on small device measurements [1]–[3], with low self-heating, and then observe a significant reduction [4]...

    [...]