A novel AlGaInP thin-film light emitting diode with omni directional reflector

Abstract

A novel AlGaInP thin-film light emitting diode (LED) with omni directional reflector structure was proposed, the corresponding fabrication process was developed. This reflector is realized by the combination of a low-refractive-index dielectric layer and a high reflectivity metal layer. The AlGaInP LED layers with dielectric-metal reflector is invertedly bonded to the GaAs submount by using 80Au-20Sn (wt%) alloy as a solder (Reflector-Submount, RS-LED), and then GaAs substrate is removed. The light that would otherwise be absorbed by the GaAs substrate is reflected by the high reflectivity dielectric-metal reflector. The optical and electrical characteristics of the RS-LED are presented and compared with the conventional AlGaInP absorbing substrate (AS) LED and AlGaInP absorbing substrate LED with distributed Bragg reflectors (DBR). A great improvement in the brightness and efficiency is observed. It is shown that the light output and lumen efficiency from the RS-LED at forward current 20mA exceed those of AS-LED by about a factor of 2.2 and 1.2, respectively, and ～2× the light output of AS-LED (DBR) and ～1.5× the lumen efficiency of AS-LED (DBR) were achieved. 194.3mcd luminous intensity from the RS-LED (at 20mA, peak wavelength 627nm) could be obtained under 20mA injection, which is 2.8 and 1.6 times higher in luminous intensity than the AS-LED (at 20mA, peak wavelength 624nm) and AS-LED(DBR) (at 20mA, peak wavelength 623nm), respectively.