Modification of strain and optical polarization property in AlGaN multiple quantum wells by introducing ultrathin AlN layer

The effects of ultrathin AlN insertion layers on the strain status, as well as optical properties of AlGaN multiple quantum wells (MQWs), were studied. A large stress variation of about -1.46 GPa can be achieved by introducing two ultrathin AlN layers at each interface between the quantum well and the barrier, thereby resulting in the fact that the degree of polarization is increased from 17.8% to 22.3% in traditional MQWs. In addition, the quantum well emission are found to become symmetric and narrower due to the suppression of compositional fluctuation. These results provide a simple technique to modify the strain field of MQWs so as to improve transverse-electric polarized emission for deep ultraviolet light emitting diodes.