We present a universal approach for determining the spontaneous polarization Psp of a wurtzite semiconductor from the emission energies of excitons bound to the different types of stacking faults in these crystals. Employing micro-photoluminescence and cathodoluminescence spectroscopy, we observe emission lines from the intrinsic and extrinsic stacking faults in strain-free GaN micro-crystals. By treating the polarization sheet charges associated with these stacking faults as a plate capacitor, Psp can be obtained from the observed transition energies with no additional assumptions. Self-consistent Poisson-Schroedinger calculations, aided by the microscopic electrostatic potential computed using density-functional theory, lead to nearly identical values for Psp. Our recommended value for Psp of GaN is -0.022+/-0.007 C/m^{2}.
@article{arxiv.1201.4294,
title = {Direct experimental determination of the spontaneous polarization of GaN},
author = {Jonas Lähnemann and Oliver Brandt and Uwe Jahn and Carsten Pfüller and Claudia Roder and Pinar Dogan and Frank Grosse and Abderrezak Belabbes and Friedhelm Bechstedt and Achim Trampert and Lutz Geelhaar},
journal= {arXiv preprint arXiv:1201.4294},
year = {2012}
}