Carrier profiling of Al-doped 4H-SiC by scanning spreading resistance microscopy

Epitaxially-grown Al-doped 4H-SiC has been studied by scanning spreading resistance microscopy. The measured current shows good quantitative agreement with the chemical Al concentration in the range $2×1016$ to $2×1020 atoms cm−3.$ Simulations of the sample temperature distribution using finite element calculations predict a maximum temperature exceeding 750 K within 100 nm of the contact region at 7.5 V dc bias for an Al doping of $1020 cm−3.$ The heating causes a significant increase in the ionization of the dopants relative to that at room temperature. Due to the strong voltage dependence, the effect can be avoided by operating below 5 V dc bias where the temperature rise is shown to be negligible for all dopant concentrations.