RAMAN DETERMINATION OF PHONON DEFORMATION POTENTIALS IN ALPHA-GAN

The effect of the built-in biaxial stress on the E(2) and A(1) (LO) q = 0 phonon modes of wurtzite GaN layers deposited by Metal Organic Vap or Phase Epitaxy on (0001) direction on sapphire substrates is studied by Raman spectroscopy. Shifts in phonon frequencies are measured, whi ch we correlate to the residual strain fields in the epilayers. Using stress calibration measurements taken from reflectance data, the biaxi al pressure coefficients of mode frequencies are determined and used t o calculate the corresponding deformation potentials. Copyright (C) 19 96 Elsevier Science Ltd