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

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 180degrees 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. (C) 2004 American Institute of Physics.