Complete in-plane polarization anisotropy of the $A$ exciton in unstrained $A$-plane GaN films Available to Purchase

Using reflectance spectroscopy, the in-plane polarization behavior of unstrained $C$- and $A$-plane GaN films is experimentally investigated. While no in-plane polarization anisotropy is observed for all three band-gap related excitons (⁠$A$⁠, $B$⁠, and $C$⁠) in unstrained $C$-plane GaN films, the $A$ exciton is completely linearly polarized perpendicular to the $c$ axis in unstrained $A$-plane GaN films. However, the $B$ and $C$ excitons are only partially polarized. This observation is in excellent agreement with results based on band-structure calculations using the Bir-Pikus Hamiltonian for the wurtzite crystal structure.