Effects of prestrained layers on piezoelectric field and indium incorporation in InGaN/GaN quantum wells

We investigated the effects of prestrained layers on piezoelectric fields and indium incorporation in blue-emitting InGaN/GaN quantum wells by using reverse-biased electroreflectance spectroscopy. We compared two sets of samples, which have identical structures except an insertion of an additional UV quantum well at the bottom of the blue-quantum well. Indium composition of quantum wells with the additional layer is larger than in the wells without the added layer. In contrast, the magnitude of the piezoelectric fields in the quantum wells with the added well is smaller even with higher In composition. The result shows that the strain in the quantum well is partially released and can be controlled by the insertion of the prestrained layer underneath.