Correlation-based study of FEA and IR thermography to reveal the 2DEG temperature of a multi-fingered high-power GaN HEMT

Abstract

High electron mobility transistors (HEMTs) based on gallium nitride (GaN) with a wide range of application potentials need to be rigorously examined for reliability to take advantage of their intrinsically extraordinary properties. The most vital parameter of the reliability, the hotspot, or Tmax, resides in the two-dimensional electron gas (2DEG) temperature profile inside the device where optical access is often restricted. The device surface temperature can be measured by widespread IR thermography with the limitation of diffraction-based IR transmission losses. However, Tmax on the sub-surface cannot be reached thermographically. Although finite element analysis (FEA)-based thermal simulations can easily reveal the 2DEG temperature profile, accuracy is tightly dependent on the realistic modeling of material/structure parameters. Because these parameters are rather sensitive to fabrication and processing, it is quite difficult to specify them accurately. To overcome these drawbacks, a method integrating both IR thermography and FEA thermal analysis is demonstrated on a fabricated high-power 40 × 360 μm packaged GaN HEMT as a proof-of-concept. Utilizing the simulation and measurement temperature profiles, a correlation algorithm is developed so that accuracy of the FEA thermal simulation is improved by calibrating the parameters specific to fabrication/process conditions by thermographic measurement. Then, it is quantitatively shown that the proposed method is able to find the 2DEG temperature profile and Tmax with an accuracy that best suits the intrinsic and extrinsic characteristics of the device under test. The method sheds light on GaN reliability engineering by providing a feasible and reliable alternative to realistically reveal hotspot information for device lifetime assessments.

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

“…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. All metallizations in the MMICs, shown in yellow in Fig.…”

“…Median-time-tofailure (MTTF) is one of the crucial parameters in terms of the device's reliability [13]- [17]. The maximum temperature (T max ) happens inside the two-dimensional electron gas (2DEG) region [18]- [21]. This temperature affects the MTTF by the following relation [21], [22]:…”

“…The drawback is that they underestimate peak channel temperature due to averaging over the active device region [25], [26]. Optical measurements such as micro-Raman and infrared (IR) thermography [27]- [30] provide information on the surface temperature [18], [19], [31], [32], not the hotspots inside 2DEG buried below the gate of each HEMT. Moreover, spatial resolution limits optical measurements due to diffraction [33].…”

Fast Unveiling of T max in GaN HEMT Devices via the Electrical Measurement-Assisted Two-Heat Source Model

“…In addition, the spatial resolution of these measurements at the T max locations in submicrometer dimensions is limited by diffraction [23]. The thermographic measurements cannot find T max alone and require additional calibrations and correlations supported by the finite element analysis (FEA) [24].…”

Decreased trap density and lower current collapse in AlGaN/GaN HEMTs by adding a magnetron-sputtered AlN gate

“…AlGaN/GaN high electron mobility transistors (HEMTs) offer high electron mobility, high saturation current, low on-resistance and high breakdown voltage, which are suitable for radio-frequency (RF) and power applications [1][2][3]. * Authors to whom any correspondence should be addressed.…”