Abstract
Self-heating effect is a major limitation in achieving the full performance potential of high power GaN power devices. In this work, we reported a micro-trench structure fabricated on the silicon substrate of an AlGaN/GaN high electron mobility transistor (HEMT) via deep reactive ion etching, which was subsequently filled with high thermal conductive material, copper using the electroplating process. From the current-voltage characteristics, the saturation drain current was improved by approximately 17% with the copper filled micro-trench structure due to efficient heat dissipation. The IDS difference between the pulse and DC bias measurement was about 21% at high bias VDS due to the self-heating effect. In contrast, the difference was reduced to approximately 8% for the devices with the implementation of the proposed structure. Using Micro-Raman thermometry, we showed that temperature near the drain edge of the channel can be lowered by approximately ~22 °C in a HEMT operating at ~10.6 Wmm−1 after the implementation of the trench structure. An effective method for the improvement of thermal management to enhance the performance of GaN-on-Silicon HEMTs was demonstrated.
Highlights
Wide-bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) are considered as outstanding materials for high frequency, high power and opto-electronic devices[1,2,3]
This reduction of IDS is due to the temperature dependence of mobility and saturation velocity. Even they were both degraded, the IDS for the high electron mobility transistor (HEMT) with Cu micro-trench was always higher than those of HEMT without micro-trench. It suggests that the performance of HEMT with Cu micro-trench was better than that of HEMT without Cu micro-trench
This study presented the results of electrical characterization, infrared thermography imaging, and Raman spectroscopy for GaN-on-Si HEMTs before and after Cu filled micro-trench fabrication
Summary
Wide-bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) are considered as outstanding materials for high frequency, high power and opto-electronic devices[1,2,3]. Numerous methods have been proposed to improve heat dissipation by using high thermally conductive substrates such as diamond and silicon carbide. Copper (Cu) filled trench structures in silicon (Si) wafer methods are being developed[21,22] This could be an effective solution for heat dissipation in vertical direction. Pavlidis et al studied only the thermal characterization using Raman thermometry and transient thermoreflectance imaging method[26] In this case, AlN with 15 μm thickness was deposited on backside of AlGaN buffer layer after trench etching. A micro-trench structure filled with high thermal conductivity material, such as copper (390 W/mK), was fabricated on the Si substrate to provide heat escape path from the hot spot. It was observed that the shift of the E2 (high) peak was lower in the Cu-deposited trench structure, which demonstrated effective heat removal
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