Thermal effects of gate connected field-plates and surface passivation on AlGaN/GaN HEMTs

Kara, Doğacan
AlGaN/GaN high electron mobility transistors (HEMTs) are widely preferred in automotive, space, and military applications due to their superior electrical and thermal properties. However, when operated in full capacity, their electrical reliability drops significantly due to electron collapse, device degradation, concentrated heating, and mechanical stresses. To increase the reliability and maximum performance of GaN HEMTs, field-plate and surface passivation technologies are used frequently. Although significant research has been done to understand the electrical effects of these structures, their true effect on thermal performance of devices is still missing in the literature. For this purpose, thermal simulations with and without gate field-plates having different thicknesses of SiO2 and Si3N4 surface passivation layers are performed. These simulations, performed using realistic Joule heating data obtained from device electrical simulations, proves that up to 6% reduction in hotspot temperature along with increased breakdown voltage can be obtained by using gate field-plate technology in GaN HEMTs operated around 4 W/mm. Since the percentage of temperature reduction is the same for devices operated at similar power densities, net temperature reduction will be higher in devices with more localized heating with higher maximum temperatures, as in the case for devices biased with more negative gate bias. Optimization studies performed as a part of this study suggests that while thick surface passivation (>200nm for Si3N4) eliminates the thermal advantages of field plate technology, thin passivation layers (<25 nm) decrease the breakdown voltage significantly and promote electron leakage. Similar results suggesting the importance of passivation thickness optimization are obtained for devices with thinner SiO2 passivation layers. Thus, significant thermal advantages are observed when gate field-plates are introduced to the device if field-plate length, passivation material and thickness are optimized based on the device operation condition.


Phase mixing in GaSb nanocrystals synthesized by nonequilibrium plasma aerotaxy
Üner, Necip Berker; Thimsen, Elijah (2020-05-01)
III-V semiconductor nanocrystals are an important class of optoelectronic materials. However, the gas-phase synthesis of these materials, especially of the stibnides, has been left relatively unexplored. In this study, we demonstrate the synthesis of free-standing GaSb nanocrystals for the first time, using a novel gas-phase process. We show that when elemental aerosols are used as precursors for Ga and Sb, the elements mix at the nanometer length scale as the aerosols pass through a nonequilibrium plasma r...
Growth, characterization and fabrication of AlGaN/GaN high electron mobility transistors on silicon carbide substrates
Emen, Ayça; Ünalan, Hüsnü Emrah; Turan, Raşit; Department of Micro and Nanotechnology (2014)
Wide bandgap semiconductor technology for electronics have received great attention over the last several years. Heterostructures composed of aluminium gallium nitride (AlGaN) and gallium nitride (GaN) are promising candidates for the fabrication of high power and high frequency devices due to their superior material properties. Silicon carbide (SiC) is the most suitable substrate for GaN growth because of its high thermal conductivity and lower lattice mismatch with GaN compared to silicon and sapphire. Th...
Nonlinear compressible finite viscoleasticity of epoxy-based polymers
Dal, Hüsnü; Gromala, P. J.; Han, B. (2019-01-01)
Epoxy-based polymers are widely used in the semiconductor industry as thermal and/or electrical interfaces and as encapsulating material. In the automotive industry, epoxy-based molding compounds (EMCs) are often used to protect not only the single IC packages but also the entire electronic control units (ECUs) (or the power modules). The stress caused by the mismatch of the coefficient of thermal expansion (CTE) between EMC and adjacent materials is one of the major causes for premature failure. In the tem...
Electrothermal Analysis of the Field-Plated AIGaN/GaN HEMTs with SiO2 Passivation
Kara, Dogacan; AKGÜN, FATMA NAZLI DÖNMEZER (2017-09-01)
AlGaN/GaN high electron mobility transistors (HEMTs) are widely used in high frequency and power applications of the space and military industries due to their high RF power densities. When operated in full capacity, reliability of GaN HEMTs drop significantly due to device degradation, electron collapse phenomena, and concentrated heating effects. Although significant research has been done to investigate the effects of passivation, field-plates on the device degradation and the electron collapse separatel...
Structural characterization of intrinsic a-Si:H thin films for silicon heterojunction solar cells
Pehlivan, O.; Yilmaz, O.; Kodolbas, A. O.; Duygulu, O.; Tomak, Mehmet (2013-01-01)
We have utilized ex-situ spectroscopic ellipsometry and HRTEM to characterize the optical and structural properties of intrinsic a-Si:H thin layer that plays a key role for the improvement of the open circuit voltage in silicon heterojunction solar cells. Intrinsic a-Si:H films were deposited on (100) p-type CZ silicon wafers by using Plasma Enhanced Chemical Vapor Deposition (PECVD) technique at 225 degrees C substrate temperature and deposition time ranges from 15 s to 1800 s. Observed changes in the imag...
Citation Formats
D. Kara, “Thermal effects of gate connected field-plates and surface passivation on AlGaN/GaN HEMTs,” M.S. - Master of Science, Middle East Technical University, 2018.