Thermal resistance optimization of GaN/substrate stacks considering thermal boundary resistance and temperature-dependent thermal conductivity

Abstract

Here, we investigate the effects of thermal boundary resistance (TBR) and temperature-dependent thermal conductivity on the thermal resistance of GaN/substrate stacks. A combination of parameters such as substrates {diamond, silicon carbide, silicon, and sapphire}, thermal boundary resistance {10-60 m 2 K/GW}, heat source lengths {10 nm-20 lm}, and power dissipation levels {1-8 W} are studied by using technology computer-aided design (TCAD) software Synopsys. Among diamond, silicon carbide, silicon, and sapphire substrates, the diamond provides the lowest thermal resistance due to its superior thermal conductivity. We report that due to non-zero thermal boundary resistance and localized heating in GaN-based high electron mobility transistors, an optimum separation between the heat source and substrate exists. For high power (i.e., 8 W) heat dissipation on high thermal conductive substrates (i.e., diamond), the optimum separation between the heat source and substrate becomes submicron thick (i.e., 500 nm), which reduces the hotspot temperature as much as 50 C compared to conventional multi-micron thick case (i.e., 4 lm). This is attributed to the thermal conductivity drop in GaN near the heat source. Improving the TBR between GaN and diamond increases temperature reduction by our further approach. Overall, we provide thermal management design guidelines for GaN-based devices. Published by AIP Publishing.

Development of GaN HEMTs Fabricated on Silicon, Silicon-on-Insulator, and Engineered Substrates and the Heterogeneous Integration

“…The increase in TBR causes an offset to the advantages offered by the substrate with high thermal conductivity due to the discontinuity of the temperature gradient in TBR layers located at the GaN substrate interface [40]. Thermal conductivity for GaN and different substrate materials at 300 K and TBR values of GaN/ substrate interface simulated in [41] are listed in Table 1. The lower TBR values of GaN on Si substrate than that of SiC substrate is mainly due to the different thermal expansion coefficient [42], the roughness of the substrate materials as well as the defect related to the growth techniques.…”

“…The high value of TBR at the interface of high thermal conductivity substrate and GaN could be reduced and has additional advantage if it has a better thermal coupling and fewer interface defects while low thermal conductivity like sapphire has a less significant influence of TBR on transporting heat [43]. [41,44]. (1994) [5].…”

The effect of low dose γ-irradiation on the optoelectric properties of n-GaN based MSM structure

“…III-nitride-based PDs are particularly commonly used in harsh environments such as space applications 2,3 Meanwhile, the wide bandgap (3.4 eV 2 ), high breakdown voltage 4 , thermal and chemical stability, and irradiation resistance introduce GaN as a suitable candidate to use in harsh and irradiated environments. 5,6 Exposure of the GaN layers with electromagnetic irradiation and/or high-energy particles has been shown to lead to the vacancy generation and defects in the crystal structure such as Ga and/or N atoms displacements from their respective lattice sites 7 . This phenomenon generates new energy levels in the bandgap, which act as scattering centers such as donor, acceptor, or recombination centers 1,8 .…”

Особенности теплопереноса в гетероструктурах Al-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N/GaN на сапфире

“…Существенное влияние на теплоперенос в гетероструктуре Al x Ga 1−x N/GaN оказывает также толщина слоя нитрида галлия [9]. Если толщина мала, то тепловой поток в этом слое распространяется в области с латеральными размерами сравнимыми с областью нагрева.…”