Schottky Barrier Lowering of Metal/4H-SiC Junction with Ultrathin Aluminum Oxynitride Interlayer

Abstract

Silicon Carbide (SiC) has been widely investigated to develop high power electronic devices as a reliable wide band gap semiconductor. The electricalcharacteristics of SiC Schottky diode depend strongly on the interface energy barrier, and a lower Schottky barrier is advantageous to improve powerefficiency and acquire fast switching. We report experimentally that the Schottky barrier of metal/4H-SiC junction is reduced significantly with an ultra-thin(down to ~1.0 nm) aluminum oxynitride (ALON) interlayer inserted at the junction interface. The ultra-thin ALON layer was deposited by using the RFmagnetron sputtering with the in-situ flashing to remove the native oxide. High-resolution transmission electron microscope (HR-TEM) images confirmed thatthe grown ALON film was amorphous. The Schottky barriers of metal/ALON/4H-SiC and metal/4H-SiC junctions were obtained by performing current-voltage(I-V), capacitance-voltage (C-V), and internal photoemission (IPE) measurements. The interface barrier was reduced by up to ~0.8 eV and the reduction wasnot related to the work-function of metal. The electrostatic potential change driven by the fixed charges in the interlayer or the Fermi-level depinningassociated with the suppression of metal-induced gap states is generally known as the origin of Schottky barrier modulation with an interlayer. However, theFermi-level pinning factor was found to remain almost unchanged in our case, implying that the surface states of 4H-SiC are NOT the main factor of theobserved Schottky barrier reduction. The fixed positive charges in the ALON thin film are presumed to cause the reduction.

*NRF-2023R1A2C1006519, NRF-2020M3F3A2A02082437