Optical polarization switching in semipolar (2021) InGaN multiple quantum wells induced by strain engineering

摘要

Semipolar (2021) InGaN/AlGaN multiple quantum wells (MQWs) with a low In content (<0.05) were coherently grown on a partially relaxed Al_xGa_(1-x)N (0 < X_(AI) < 0.4) layer. As X_(AI) increased from 0.15 to 0.38, the degree of optical polarization measured by photoluminescence at 13 K changed from 0.49 to -0.24, where (-) indicates the change in the dominant polarization direction from [1120] to [1014]. Regardless of X_(AI) and thickness, no polarization switching was observed if Al_xGa_(1-x)N was fully strained to the GaN substrate. Band structure modeling based on the k•p method implies that the polarization switching is associated with strong valence band mixing induced by the one-dimensional strain relaxation in AlGaN, which leads to a significantly stronger compressive strain in MQWs along [1014] relative to [1120]. These results demonstrate that the optical polarization switching in semipolar MQWs can be controlled by engineering the strain state of the underlying layer.