研究目的
To investigate the degradation mechanisms of GaN HEMTs under high temperature operation stress, focusing on thermal performance and failure modes.
研究成果
The HTO stress experiments revealed significant degradation in DC characteristics and a 41% increase in junction temperature. The primary cause is the degradation of the die attach layer, with void expansion and through-hole formation leading to worse heat dissipation, increased thermal resistance, and accelerated device performance degradation. Improvements in die attach layer quality and packaging processes are essential for enhancing high temperature reliability of GaN HEMTs.
研究不足
The study is limited to specific commercial GaN HEMT devices and HTO stress conditions; results may not generalize to other devices or stress scenarios. The transient thermal resistance testing may be affected by electrical interference, requiring rectification. Cryogenic utilities were not applied, which might affect defect investigation accuracy.
1：Experimental Design and Method Selection:
High temperature operation (HTO) stress experiments were conducted on commercial AlGaN/GaN HEMT devices to study degradation. Transient thermal resistance testing technique based on forward junction voltage and structural function analysis was used for thermal performance analysis.
2：Sample Selection and Data Sources:
Industrial GaN HEMTs devices with specific epitaxial structures (GaN buffer layer, SiC substrate, GaN layer, AlN spacer layer, GaN cap layer, AlGaN barrier layer, SiNx passivation) were used. Gate width
3：5mm, gate length 5μm, gate-drain spacing 5μm, gate-source spacing 2μm. List of Experimental Equipment and Materials:
Agilent B1500A semiconductor parameter analyzer for electrical characterization, T3ster thermal resistance tester for transient thermal resistance testing, three-dimensional X-ray imaging for structural analysis.
4：Experimental Procedures and Operational Workflow:
HTO experiments performed at VDS=28V, IDS=200mA, VGS=-
5：9V at environmental temperatures of 160°C for 291h, 180°C for 216h, 190°C for 478h (total 985h). Electrical characterization and thermal resistance testing conducted before and after stress. Calibration of Schottky junction voltage in temperature-controlled oil tank to obtain k-factor. Heating power applied (4W with VGS=-6V, VDS=8V, IDS=500mA), then cooling curve measured. Structural function analysis performed on cooling curves. Data Analysis Methods:
Analysis of I-V curves, transconductance, threshold voltage shifts, gate leakage currents. Use of semi-infinite plate model to deduce junction temperature. Structural function analysis to determine thermal resistance distribution. Three-dimensional X-ray imaging to confirm die attach layer degradation.
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