Accuracy of polarization field measurements by electron holography in InGaN quantum wells

Abstract

We thoroughly investigate two methods for estimating electric field strength across semiconductor heterostructure quantum wells from electron holograms. Due to the small width of quantum wells these holograms must often be taken under dynamical diffraction conditions, since projection effects forbid the investigation under larger tilt angles. We especially investigated the robustness of the evaluation methods against dynamical diffraction artifacts due to excitation conditions and strain, artifacts due to the material contrast, as well as limited resolution effects. For this we developed ways to incorporate polarization effects into combined strain and multislice simulations. It turns out that errors estimated from detection noise of single measurements alone mostly underestimate the true error, since variation due to hardly controlled diffraction effects and measurement details often prevails.