Quantification of Biaxial Strain Effect on the Mean Inner Potential of InxGa1-xN

Off-axis electron holography enables a direct access to electrostatic potentials in semiconductor heterostructures, but its quantitative interpretation relies critically on accurate mean inner potential (MIP) values. Here, we combine off-axis electron holography with self-consistent electrostatic simulations to extract the MIP of InxGa1-xN/GaN heterostructures. By calibrating the surface Fermi-level pinning, experimental phase-shift profiles are quantitatively matched to simulations, allowing the MIP difference between GaN and InxGa1-xN to be determined. The derived MIP values deviate systematically from the linear interpolation of unstrained MIP values of GaN and InN, indicating a significant strain contribution. This strain effect is captured by an analytical strain-dependent model that reproduces the experimental MIP trend and yields a large intrinsic difference between the unstrained MIP values of GaN and InN of 3.0±1.7 V, which is consistent with density functional theory calculations. The approach provides a practical and computationally efficient route for determining strain-dependent MIP values, facilitating quantitative electron microscopy studies of strained semiconductor heterostructures.