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 In(0.13)Ga(0.87)N/GaN quantum wells has been studied by resonant Raman scattering. The A1 (LO) phonon of In(0.13)Ga(0.87)N 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 In(0.13)Ga(0.87)N 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 A1 (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.