Pulsed laser atom probe tomography (APT) of InxGa1−xN single quantum well (SQW) grown on semipolar (101¯1¯) GaN orientation estimates the interior atomic composition within the SQW at 6.5±0.7 at. % In, 46.2±0.7 at. % Ga, and 47.3±0.7 at. % N. The atom probe analysis is performed in both “top-down” and “cross-section” orientations. Self-consistent Schrödinger–Poisson simulation employing structural and compositional parameters obtained from APT results estimates the polarization field within the SQW at 720 kV/cm. A statistical method for the evaluation of indium homogeneity within the SQW is also considered.