Solution for efficient cooling of power Ga2O3 semiconductor devices
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Gallium oxide (Ga2O3) is a promising material for manufacturing of semiconductor devices. The main advantage of Ga2O3 is its large energy gap and the resulting high breakdown field. This allows the use of Ga2O3 epitaxial films for processing of high voltage devices (transistors, diodes), while the wide bandgap opens up the possibilities of its use for optoelectronic components operating in the deep UV region.
However, one of the main disadvantages of Ga2O3 is its low thermal conductivity, which limits the performance range as well as the lifetime of Ga2O3 based devices. A possible solution of Ga2O3 low thermal conductivity have addressed in a recent study our colleagues. The low thermal conductivity can be minimized by growing Ga2O3 layers on SiC substrates, which in turn have high thermal conductivity while providing a suitable crystalline structure for Ga2O3 epitaxial growth. Using a combination of thermal measurements and simulation, we found that placing thin Ga2O3 layers on SiC provides a significant reduction in transistor self-heating compared to structures prepared on bulk Ga2O3 substrate (up to almost 30× for thickness < 2 μm). Further, no significant thermal barrier is formed between the Ga2O3 layers and the SiC substrate, which would fundamentally hinder the dissipation of generated heat. Our work opens up new possibilities of integration of Ga2O3 with SiC substrates in order to optimize the thermal performance of power Ga2O3 semiconductor devices.
Fig. 1: Surface of Ga2O3 film imaged by atomic force microscope (left) and simulation result of self-heating in depletion field-effect transistor (MOSFET) fabricated from our Ga2O3 layers on SiC (right). The simulation shows that while maintaining a channel thickness of 2 μm, the self-heating of the transistor is negligible compared to higher thicknesses, or the case of a typically used Ga2O3 substrate instead of SiC.
Written by: Fedor Hrubišák
More info: Hrubišák, F., et al.: Heteroepitaxial growth of Ga2O3 on 4H-SiC by liquid-injection MOCVD for improved thermal management of Ga2O3 power devices, J. Vacuum Sci Technol. A 41 (2023) 042708.