Influence of quantum well design on light polarization switching in AlGaN ultraviolet emitters

Abstract

Polarization properties from AlGaN quantum well (QW) strongly determine the efficiency of deep ultraviolet (UV) light-emitting diodes (LEDs), hence knowing the critical Al-content at which the light polarization switches is essential for high-efficiency deep UV LED designs. This work theoretically investigates the influence of QW design on the light polarization switching in AlGaN-based UV LEDs. The physics analysis by using the self-consistent 6-band k·p model shows that the Al-content for valence subbands crossover presents an increasing trend as AlGaN QW thickness increases with consideration of polarization electric field, carrier screening effect and strain state. On the other hand, the critical Al-content where the transverse-electric-polarized spontaneous emission recombination rate (Rsp) is equal to the transverse-magnetic-polarized Rsp has the maximum value at the QW thickness of ∼1.5 nm. The difference between the two types of critical Al-contents can be explained by the quantum confined stark effect and the band mixing effect. The light polarization properties from reported AlGaN-based UV emitters show a similar trend to our theoretical results on critical Al-contents, indicating the importance on the understanding of QW design for high-efficiency deep-UV emitters.