A lattice polarity determination method for GaN is demonstrated, which is based on a capability of modulation spectroscopy for the assignment of electric-field directions performed nondestructively using simple optical setups. A strong spontaneous polarization induces an upward band bending toward +c surfaces and a downward but weaker bending toward -c surfaces for typical films with small residual strains and electron densities. This difference is distinguishable in terms of the spectral-phase flip, utilizing photoreflectance, and electroreflectance. Quantitative analysis revealed the exciton dissociation at a high-field region of +c surfaces consistent with the band profile derived as a solution of Poisson equation.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)