Raman study of the nitrided GaAs thin layers

Abstract

The properties of the nitrided GaAs thin layers have been investigated by using Raman spectroscopy. The nitrided GaAs thin layers were prepared by irradiating electron-cyclotron resonance (ECR) nitrogen plasma at various substrate temperatures from room temperature to 600 degrees C. Raman measurements have shown that not only are the longitudinal-optical (LO) and transverse-optical (TO) phonon modes shifted down in frequency, but also the LO-TO splitting decreases as the nitridation temperature increases. It is believed that the origin of the frequency shifts is the changes in effective charge and the strain effects due to defects included in the nitrided GaAs thin layers. The bandwidth for the LO-phonon mode for the sample nitrided at 600 degrees C is the largest, which means that the nitridation at high temperature causes more disordered surface structure. We have estimated several physical parameters in the nitrided GaAs thin layers, such as the fraction of defects, the strains, and the correlation length from the measured Raman spectra. [S0163-1829(98)05719-1].