Solution for efficient cooling of power Ga2O3 semiconductor devices

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.