Piezoelectric, electro-optical, and photoelastic effects in $InxGa1−xN/GaN$ multiple quantum wells

We present microphotoluminescence (PL) and micro-Raman measurements with varying the applied electric field in $InxGa1−xN/GaN$ multiple quantum wells (MQWs). The $InGaN A1(LO)$ phonon was found to show a redshift in frequency with the increase of applied electric field. And, a blueshift in PL spectra has been observed when the applied electric field was increased. Quite interestingly, the change in the refractive index was also observed, which was determined accurately from the interference pattern shown in the emission spectra. This finding correlates very well with the blueshift of PL spectra and the redshift of the $InGaN A1(LO)$ phonon. Based on the stress change induced by the compensation between piezoelectric and external fields, our results firmly establish that strong electro-optical and photoelastic effects do exist in $InxGa1−xN/GaN$ MQWs, which is important in the design of optoelectronic devices.