High-power AlGaN/GaN HFETs on Si substrates for power-switching applications

Epitaxial growth technology for GaN devices on large-diameter Si substrate has been studied in this paper, which is essential for device cost reduction. In an effort to improve the buffer breakdown voltage for increasing the breakdown voltage of the device, carbon concentration in the GaN layer was controlled to find that the carbon concentration significantly contributed to buffer breakdown voltage improvements. Device performance was evaluated for the devices with an AlGaN/GaN HFET structure on Si substrate, and it was shown that the performance was equivalent to that of the device on sapphire substrate. A large-area device having this structure was fabricated in order to confirm its potential as a power device, and a current capacity of 120 A or more and a breakdown voltage of 1.8 kV were achieved. On the other hand, with respect to the problematical issue of current collapse in GaN HFETs, the HFET structure on Si substrate has resulted in a significant improvement compared with the structure on sapphire substrate, thus realizing a high-performance device that does not show a salient current collapse up to 1 kV.