A Roadmap for Building Thermal Models for AlGaN/GaN HEMTs: Simplifications and Beyond

Abstract

AlGaN/GaN based high electron mobility transistors (HEMTs) have been intensively used due to their high-efficiency power switching and large current handling capabilities. However, the high power densities and localized heating in these devices form small, high temperature regions called hotspots. Analysis of heat removal from hotspots and temperature control of the entire device is necessary for the reliable design of HEMT devices. For accurate analysis of heat transfer using thermal simulations in such devices with heat transfer occurring at different length scales, a roadmap is needed. For this purpose relative importance of different heat transfer modes in removing heat from devices with different substrate materials, operating at different power densities while different boundary conditions are analyzed using two and three-dimensional COMSOL Multiphysics simulations. Results give the relative importance of different parameters on the heat removal mechanism from devices and provide a roadmap for building simpler yet still accurate thermal models for AlGaN/GaN HEMTs and similar devices.

Unveiling Tmax Inside GaN HEMT Based X-Band Low-Noise Amplifier by Correlating Thermal Simulations and IR Thermographic Measurements

“…3(b), MMIC die is attached to Copper Molybdenum Copper (CMC) package using a die-attach material (DAM). Halfsymmetric boundary conditions, defined as isothermal (T base = 85 °C) at the bottom and adiabatic on all other surfaces, are selected [43], [44]. The effect of the radiative and the convective heat transfer mechanisms is negligible compared to conductive heat transfer; therefore, the radiative and the convective heat transfer mechanisms are not utilized [44].…”

“…Halfsymmetric boundary conditions, defined as isothermal (T base = 85 °C) at the bottom and adiabatic on all other surfaces, are selected [43], [44]. The effect of the radiative and the convective heat transfer mechanisms is negligible compared to conductive heat transfer; therefore, the radiative and the convective heat transfer mechanisms are not utilized [44]. The thermal conductivities of the materials used in the simulations are tabulated in Table I [18], while the geometry of the device and its components and layers are mentioned in Table II.…”

“…The distance "d" between two HEMTs is 1.125 mm. The Thermal conductivity (W/mK) GaN [44], [48] T 130x(300/T) 1.4 SiC [44], [48] T 430x(300/T) zoomed view of one of the HEMTs is shown in Fig. 3(c).…”

Efficient 3D-TLM Modeling and Simulation for the Thermal Management of Microwave AlGaN/GaN HEMT Used in High Power Amplifiers SSPA

“…For the thermal analysis of a multi-fingers AlGaN/GaN HEMT die, Figure 4 shows the dimension geometry, with its geometrical parameters listed in Table 2 [40]. The epitaxial layers were grown by MOCVD on the semi insulating SiC substrates.…”

“…However, the material density ρ (kg/m 3 ) and specific heat C p (J/kg·k) are not sensitive to temperature variation, and they can be used for simulation as constants. A range of the related material properties is shown in Table 3 [40].…”