Quantitative measurements of internal electric fields with differential phase contrast microscopy on InGaN/GaN quantum well structures: Measurements of internal electric fields

Piezoelectric and spontaneous polarization play an essential role in GaN-based devices. InGaN quantum wells (QWs) in GaN host material, especially grown along the polar c-direction, exhibit strong internal fields in the QW region due to the indium-induced strain. An exact knowledge of the electric fields is essential, since they are one of the factors limiting the performance of green LDs and LEDs. Differential phase contrast in a scanning transmission electron microscope enables direct, local, and quantitative measurements of these electric fields. For a multi-QW sample, it was possible to determine the piezoelectric field in the range of 43–67 MV m−1 with a resolution of 10 MV m−1 (≡ 10 mV nm−1).