Interface Energy Barrier Inhomogeneity of Pt/4H-SiC Schottky Junction Probed by Solid-State Device Version of Ballistic Electron Emission Spectroscopy

We propose a novel approach using the solid-state device version of ballistic electron emission spectroscopy (BEES) to estimate the spatial inhomogeneity of the interface energy barrier at metal/semiconductor and metal/insulator/semiconductor junctions without performing local microscopic analysis. The planar BEES measurements, performed on the hot electron transistor structure of Pt/AlOx/Pt/4H-SiC, reveal the significant threshold roll-off in BEES spectra when the Pt/4H-SiC junction is reverse-biased, which cannot be explained by image-force lowering. To address this anomaly, we incorporate the Tung model describing the potential landscape at inhomogeneous metal/semiconductor interface into the Bell-Kaiser theory, the standard framework for interpreting local BEES spectra. Our updated theory predicts two key outcomes: (1) The barrier inhomogeneity leads to the gradual turn-on of planar BEES spectrum near the threshold. (2) While the barrier inhomogeneity influences the shape of planar BEES spectrum, the peak position in the second derivative of the spectrum still corresponds to the mean barrier height at sufficiently low temperatures. By fitting the second derivative of measured BEES spectrum to the corresponding curve derived from the updated theory, we can probe the barrier inhomogeneity rapidly and quantitatively without the need for time-consuming microscopic investigations.