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

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 multiQW sample, it was possible to determine the piezoelectric field in the range of 43-67MVm(-1) with a resolution of 10MVm(-1) (= 10mVnm(-1)). (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei