Determining phonon deformation potentials of hexagonal GaN with stress modulation

In this work, phonon deformation potentials for E 2 H and A 1 ( L O ) phonons of epitaxial hexagonal GaN thin films grown by metalorganic chemical vapor deposition on Si (111) substrate were precisely determined with a stress modulation method, which was achieved via coin-shaped patterning of an originally flat film. By changing the size of patterned coin-shaped islands, the original biaxial stress in the flat film was reduced to different levels at the island centers, which was analyzed by finite element calculations. The proposed stress modulation method allows one to carry out a large number of Raman scattering tests, thereby leading to reliable results. With this method, the Raman biaxial pressure coefficients of E 2 H and A 1 ( L O ) phonons of GaN were determined to be 4.47 cm − 1 / GPa and 2.76 cm − 1 / GPa , respectively.