Three-dimensional simulation of scanning tunneling microscopy for semiconductor carrier and impurity profiling

摘要

Scanning tunneling microscopy for semiconductor carrier profiling is simulated in three dimensions. By solving the tunnel currents between a probe tip and a sample consistently with the current continuity equations, current–voltage characteristics in good agreement with measurements are obtained. Critical differences from potential-based calculations are observed under depletion and inversion conditions. By preparing a current–concentration table from samples with uniform concentrations, the carrier profile in p-n junction samples can be extracted by estimating the concentrations at each position. It is revealed that the tunnel current is spread around the depletion region of a p-n junction, which affects the results dramatically. When a proposed simulation is iteratively used with measurements, impurity profile extraction is possible even in the depletion region.