Abstract
A three-dimensional thermal simulation investigation for the thermal management of GaN-on-SiC monolithic microwave integrated circuits (MMICs) of consisting multi-fingers (HEMTs) is presented. The purpose of this work is to demonstrate the utility and efficiency of the three-dimensional Transmission Line Matrix method (3D-TLM) in a thermal analysis of high power AlGaN/GaN heterostructures single gate and multi-fingers HEMT SSPA (solid state power amplifiers). The self-heating effects induce thermal cross-talk between individual fingers in multi-finger AlGaN/GaN that affect device performance and reliability. Gate-finger temperature differences only arise after a transient state, due to the beginning of thermal crosstalk which is attributed to the finite rate of heat diffusion between gate fingers. The TLM method accounts for the real geometrical structure and the non-linear thermal conductivities of GaN and SiC in order to improve the realistic calculations accuracy heat dissipation and thermal behavior of the device. In addition, two types of heat sources located on the top of GaN layer are considered in thermal simulations: Nano-scale hotspot as a pulsed wave heat source under gate and micro-scale hotspot as a continuous wave heat source, between gate and drain. Heat diffusion however, occurs not only between individual gate fingers (inter-finger) in a multi-finger HEMT, but also within each gate finger (intra-finger). To compare results, a Micro-Raman Spectroscopy experience is conducted to obtain a detailed and accurate temperature distribution. Good agreement between the microscopic spectral measurement and TLM simulation results is observed by accepting an error less than 2.2% relative to a maximum temperature. Results show that the 3D-TLM method is suitable for understanding heat management in particular for microwave devices AlGaN/GaN HEMTs SSPA amplifier. TLM method helps to select and locates the expected hot spots and to highlight the need of thermal study pre-design in order to minimize the system-level thermal dissipation and lead therefore to higher reliability.
Highlights
IntroductionThe GaN HEMTs (High Electron Mobility Transistor) application is currently growing due to its superior properties, such as high breakdown voltage and high cut-off frequency, which allow designing power switches devices and high efficiency power amplifiers for generation wireless communication, satellite communication and radar systems [1]
The GaN HEMTs (High Electron Mobility Transistor) application is currently growing due to its superior properties, such as high breakdown voltage and high cut-off frequency, which allow designing power switches devices and high efficiency power amplifiers for generation wireless communication, satellite communication and radar systems [1].The heterojunction AlGaN/GaN-based HEMTs have been recognized as the most promising devices for high-power applications at microwave and millimeter-wave frequency range
Its high thermal conductivity allows these high-power densities to be efficiently dissipated for realistic drain efficiencies to prevent the extreme channel temperatures that would occur due to self-heating with other substrates technologies [8,9]
Summary
The GaN HEMTs (High Electron Mobility Transistor) application is currently growing due to its superior properties, such as high breakdown voltage and high cut-off frequency, which allow designing power switches devices and high efficiency power amplifiers for generation wireless communication, satellite communication and radar systems [1]. Its high thermal conductivity allows these high-power densities to be efficiently dissipated for realistic drain efficiencies to prevent the extreme channel temperatures that would occur due to self-heating with other substrates technologies [8,9]. We analyzed the thermal characteristics of AlGaN/GaN HEMT’s single gate finger, multi-gate finger, and multi-material We focused in this analysis on a 3-D distribution of the temperature, thermal behavior, self-heating and channel temperature. Scattered thermal pulses are the reflected pulses 0 T calculated from a circuit analysis of the where, Z is the characteristic impedance: Z = 3∆t/C and I(n) is the heat source generator and Y is the admittance which is given by: Y= 2 + 2 + 2 Rx + Z Ry + Z Rz + Z. Localized self-heating increases the channel temperature and happens in a region near the gate contact inside the most majority multi-finger HEMT structure
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