Enhanced Light Extraction in AlInGaN UV Light-Emitting Diodes by an Embedded AlN/AlGaN Distributed Bragg Reflector

A novel kind of AlInGaN ultraviolet (UV) light-emitting diode (LED) with an embedded AlN/Al0.3Ga0.7N distributed Bragg reflector (DBR) is proposed to enhance light extraction efficiency (LEE). The simulation technique we adopt to calculate the LEE of LEDs is based on the theory of spontaneous emission in a layered medium, the well-known mode-matching technique and the scattering matrix approach. The AlN/Al0.3Ga0.7N DBR was intentionally designed to have peak reflectivity at the LED emission wavelength and the optical properties of the DBR were simulated by using the transfer matrix method. A high LEE of 45.7% at 370nm wavelength was predicted for a proposed AlInGaN UV LED consisting of 24 periods of the AlN/Al0.3Ga0.7N DBR, which is 1.5 times of that of the conventional AlInGaN UV LED. The investigation shows that the AlN/Al0.3Ga0.7N DBR grown on GaN templates with sapphire as a substrate by MOCVD can enhance the LEE effectively and would be very promising for the fabrication of high performance GaN-based UV LEDs.