No abstract

Ultrahigh channel mobility is demonstrated for 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with Al2O3 gate insulators fabricated at low temperatures by metal-organic chemical-vapor deposition. Relatively high field effect channel mobility of 64cm2∕Vs is obtained when the Al2O3 gate insulator is deposited at 190°C. Furthermore, extremely high field effect mobility of 284cm2∕Vs was obtained for a MOSFET fabricated with an ultrathin thermally grown SiOx layer inserted between the Al2O3 and SiC.

We have fabricated and characterized MOS capacitors and lateral MOSFETs using Al2O3 as a gate insulator. Al2O3 films were deposited by metal-organic chemical vapor deposition (MOCVD) at temperatures as low as 190 oC using tri-ethyl-aluminum and H2O as precursors. We first demonstrate from the capacitance – voltage (C-V) measurements that the Al2O3/SiC interface has lower interface state density than the thermally-grown SiO2/SiC interface. No significant difference was observed between X-ray photoelectron spectroscopy (XPS) Si 2p spectrum from the Al2O3/SiC interface and that from the SiC substrate, which means the SiC substrate was not oxidized during the Al2O3 deposition. Next, we show that the fabricated lateral SiC-MOSFETs with Al2O3 gate insulator have good drain current – drain voltage (ID-VD) and drain current – gate voltage (ID-VG) characteristics with normally-off behavior. The obtained peak values of field-effect mobility (μFE) are between 68 and 88 cm2/Vs.

Low temperature deposition of HfO2 films on 4H-SiC(0001) substrates by pulse introduced metalorganic chemical vapor deposition (MOCVD) using tetrakis-diethylamido-hafnium [Hf[N(C2H5)2]4, (TDEAH)] and H2O has been investigated. HfO2 films with relatively low leakage current density of 10-4 A/cm2 were obtained even at a deposition temperature as low as 190 °C. We demonstrate that the HfO2/SiC interface, where the HfO2 was deposited at 190 °C, has lower interface state density than a typical thermally-grown SiO2/SiC interface. It is also shown by X-ray photoelectron spectroscopy (XPS) that the HfO2/SiC structure fabricated at 190 °C has lower SiOx count than the HfO2/SiC structure fabricated at 400 °C.