In Situ Mapping of Space Charge Region Activation Dynamics in SiC/Si-Based Heterostructures by KPFM/STS: Role of Interface State Recharging

This work presents a novel combined method for the in situ analysis of electronic properties of SiC/Si heterojunctions with submicron resolution (30 nm), integrating Kelvin probe force microscopy (KPFM) and scanning tunneling spectroscopy (STS). For the first time, we have experimentally discovered a threshold activation effect of the space charge region (SCR) with a characteristic delay time of 2.3 ± 0.5 s and nonexponential work function relaxation (τ = 35 ± 2 s, β = 0.65 ± 0.05), indicating an energy distribution of interface states with a characteristic energy of 0.12 eV. A quantitative correlation between interface morphology and spatial distribution of the density of states ( $${{D}_{{{\text{it}}}}}$$ ) has been established, showing a fivefold increase of $${{D}_{{{\text{it}}}}}$$ in dislocation areas (>5 × 1012 cm–2 eV–1) compared to atomically smooth terraces. A physical model linking the $${{D}_{{{\text{it}}}}}(x)$$ gradient with nonlinear band curving in the depletion region has been developed. Specific engineering solutions for radiation-hard converters are proposed: contact geometry optimization (30% reduction of fringe fields), $${\text{A}}{{{\text{l}}}_{{\text{2}}}}{{{\text{O}}}_{{\text{3}}}}$$ passivation (40% Schottky barrier reduction), and doping for relaxation time control. The results enable the targeted improvement of betavoltaic cell efficiency and the sensitivity of ionizing radiation detectors.