Nanoscale Mapping of Sub‐Gap Electroluminescence from Step‐Bunched, Oxidized 4H‐SiC Surfaces

Abstract

Scanning tunneling luminescence microscopy (STLM) and scanning tunneling spectroscopy (STS) are used to study step‐bunched, oxidized 4H‐SiC surfaces prepared using a silicon melt process. The step‐bunched surface consists of atomically smooth terraces parallel to [0001] crystal planes, and rougher risers containing nanoscale steps formed by the termination of these planes. The striking topography of this surface is well resolved with large tip biases around −8 V and set currents less than 1 nA. Hysteresis in the STS spectra is preferentially observed on risers, suggesting that they contain a higher density of surface charge traps than the terraces where hysteresis is more frequently absent. Similarly, intense sub‐gap light emission centered around 2.4 eV is observed mainly on the risers albeit only with larger tunneling currents equal to or greater than 10 nA. The surface‐oxide‐related origin of this emission is reinforced by comparing tunneling electroluminescence spectra on the 4H‐ and 6H‐polytypes, and by the observation of a drastic reduction in emitted intensity after removal of the oxide in buffered HF. These results demonstrate the capability of STLM for the observation of surface impurities and defects responsible for sub‐gap light emission with spatial resolutions approaching the length scale of the defects themselves.

From dissolution to controlled macrostepping of 4H-SiC during liquid Si-induced structuring in a sandwich configuration

“…This is mainly attributed to electrically active defects at the SiO 2 /SiC. While the origin of these interface defect states is still under debate, there is a conjunction of experimental observations correlating them to the micro-stepped morphology of the 4°off epitaxial surfaces used [3,4]. Such morphology is expected to directly impact the creation of the SiO 2 /SiC interface by eventually initiating non-ideal oxidations and non stoichiometric near-interface regions [5].…”