Electroreflectance study on the polarization field in InGaN/AlInGaN multiple quantum wells

Abstract

We present an electroreflectance investigation on the polarization field in InGaN/AlInGaN quantum wells (QWs) grown on GaN, in which the AlInGaN barrier is lattice-matched to the GaN substrate. Due to the quantum-confined Stark effect on the QWs, the bias-dependent spectra reveal a paraboliclike energy shift, an intensity minimum, and an 180° phase change at the flat-band voltage. By using this technique, the polarization field can be measured precisely. We found that the polarization field in the InGaN/AlInGaN QW is reduced significantly as compared with that in the InGaN/GaN system. The reduced polarization field is attributed to the contribution of spontaneous polarization in the quaternary barrier, which tends to compensate the piezoelectric polarization in the InGaN QWs.