Measurement of the piezoelectric field across strained InGaN GaN layers by electron holography

Electron holography at 200 kV in a field emission transmission electron microscope has been used to profile the piezoelectric held across a GaN/1.5 nm In0.52Ga0.48N/GaN single quantum well structure. By using cross-sectional samples under conditions where surface relaxation effects were negligible, a local decrease in potential of 0.6 +/- 0.2 V was measured across the InGaN layer in the [0001] direction, implying a local piezoelectric field E-[000 (1) over bar]] of 4 MV cm(-1), in agreement with bulk estimates. The potential of the technique for profiling non-uniform fields and other GaN based layers is assessed. (C) 1999 Elsevier Science Ltd. All rights reserved.