Piezoelectric fields of localized states in trapezoidal InGaN quantum wells

The piezoelectric fields of localized states in trapezoidal InGaN quantum wells (QWs) were investigated using electric field dependent electroreflectance (ER) spectroscopy. From the energy shift in ER peak in a bias range from 0 to −24 V, the piezoelectric field of the dominant QWs was estimated to be −1.22 MV/cm. In contrast, the localized states exhibited a piezoelectric field that was about 30%–60% weaker than for the dominant QW states. The reduced piezoelectric field in the localized states can be attributed to the partial release of compressive strain in the local InGaN regions, along with a relative reduction in the effective reverse-bias. The relative decrease in the reverse-bias can be explained by the voltage drop in the localized states that is caused by an increase in the leakage current under a reverse-bias.