关键词: GaN field effect transistor, reverse conduction, integrated diode, turn-on voltage

Abstract: A vertical GaN field-effect transistor with an integrated self-adapted channel diode (CD-FET) is proposed to improve the reverse conduction performance. It features a channel diode (CD) formed between a trench source on the insulator and a P-type barrier layer (PBL), together with a P-shield layer under the trench gate. At forward conduction, the CD is pinched off due to depletion effects caused by both the PBL and the metal-insulator-semiconductor structure from the trench source, without influencing the on-state characteristic of the CD-FET. At reverse conduction, the depletion region narrows and thus the CD turns on to achieve a very low turn-on voltage ($V_{\rm F}$), preventing the inherent body diode from turning on. Meanwhile, the PBL and P-shield layer can modulate the electric field distribution to improve the off-state breakdown voltage (${\rm BV}$). Moreover, the P-shield not only shields the gate from a high electric field but also transforms part of $C_{\rm GD}$ to $C_{\rm GS}$ so as to significantly reduce the gate charge ($Q_{\rm GD}$), leading to a low switching loss ($E_{\rm switch}$). Consequently, the proposed CD-FET achieves a low $V_{\rm F}$ of 1.65 V and a high ${\rm BV}$ of 1446 V, and $V_{\rm F}$, $Q_{\rm GD}$ and $E_{\rm switch}$ of the CD-FET are decreased by 49%, 55% and 80%, respectively, compared with those of a conventional metal-oxide-semiconductor field-effect transistor (MOSFET).

Key words: GaN field effect transistor, reverse conduction, integrated diode, turn-on voltage