Normally-off hydrogen-terminated diamond field effect transistor with yttrium gate

Abstract

The normally-off Yttrium (Y) gate hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with 5 nm Al2O3 dielectric layer has been successfully fabricated and evaluated in this work. The threshold voltage is extracted to be - 0.21 V at drain source voltage of −10 V, and the normally-off mode should be caused by the low work function of Y. The saturated drain current (IDSsat) is - 16.14 mA/mm obtained at gate voltage (VGS) of - 2.5 V with 4 μm gate length and 100 μm gate width. The value of IDSsatIDSmax is relatively high compared with other normally-off H-terminated diamond FETs at the same gate voltage, and this is ascribed to the well-preserved two-dimensional hole gas channel. The maximum transconductance of the fabricated device is 7.97 mS/mm. The current on/off ratio is about 7 orders of magnitude with a subthreshold swing of 150 mV/dec. The maximum effective mobility is 233.08 cm2/V. The results contribute to the development of normally-off H-terminated diamond FETs significantly.