Joint evaluation of internal quantum efficiency and light extraction efficiency for AlGaN-based deep ultraviolet LEDs considering optical polarization properties

Abstract

In this work, a joint evaluation method for the internal quantum efficiency (IQE) and light extraction efficiency (LEE) for AlGaN-based deep ultraviolet (DUV) light emitting diodes (LEDs) is proposed by fully considering the optical polarization properties. In this method, the IQE curve varying with the forward current can be reconstructed from a few measurement data at a small injection level. The corresponding LEE can be determined using the composition of spontaneous emission light with transverse electric and transverse magnetic components at different forward currents. The proposed method is applied for the efficiency evaluation of the AlGaN-based LED sample and verified by comparing with the EQE result deduced from the measured light output power-current (L-I) characteristic. It is demonstrated that the very low EQE and significant efficiency droop is from not only IQE but also LEE for AlGaN-based DUV LEDs.