Effect of strain and associated piezoelectric fields in InGaN GaN quantum wells probed by resonant Raman scattering

The influence of pseudomorphic strain and resulting piezoelectric fields on In0.13Ga0.87N/GaN quantum wells has been studied by resonant Raman scattering. The A(1)(LO) phonon of In0.13Ga0.87N pseudomorphically strained to GaN is found to be downshifted in frequency by only 3 cm(-1) with respect to GaN, which gives evidence for a near cancellation between the much larger frequency downshift of 10 cm(-1) reported for unstrained In0.13Ga0.87N and a high-frequency shift of the A(1)(LO) phonon induced by the in-plane compressive strain. For excitation in resonance with the fundamental interband transition of the InGaN well, the intensity of first- and second-order scattering by the InGaN A(1)(LO) phonon was found to decrease with decreasing excitation power density, and thus increasing strength of the piezoelectric field. This finding is explained by a quenching of the excitonic enhancement in the resonance profile by the piezoelectric field. (C) 1999 American Institute of Physics. [S0003-6951(99)03725-0].