Polarization relaxation in InGaN/(In)GaN multiple quantum wells

Abstract

In this paper, we report the polarization reduction of polarization field strength in InGaN/(In)GaN multiple quantum wells (MQWs), which is called polarization relaxation because its behavior is somehow similar to the strain relaxation in MQWs. It is found that the polarization is dependent not only on the MQWs structure, i.e. indium content in the well and barriers and the well thickness, but also on the growth conditions such as growth temperature. The threshold of polarization relaxation is related to the indium content in the quantum barriers. Further analysis shows that the strain energy in MQWs has significant influence on the degree of polarization relaxation. The critical layer thickness for the polarization relaxation is lower than that for the lattice relaxation, indicating that the polarization relaxation happens prior to the lattice relaxation. Moreover, the degree of polarization relaxation has a dependence on the growth temperature, indicating that the polarization relaxation can be enhanced by the thermal energy during epi-growth. The mechanisms behind this phenomenon is discussed.