Light Output Enhancement of AlGalnP Light Emitting Diodes with Nanopores of Anodic Alumina

In this paper, we describe the improvement in the light extraction efficiency of AlGalnP light-emitting diodes (LEDs) upon use of a porous anodic alumina (PAA) film and pore widening. Acting as an intervening layer between air and the GaP window layer, PAA increased the critical angle to reduce the internal light reflection of LEDs. The nanopores of the PAA film provided a rough surface that enhanced the light output extraction. These factors resulted in the LEDs with PAA films exhibiting a light output power 29% higher than that of a conventional LED (without PAA film). Furthermore, following a pore-widening treatment for 40 min, the light output improvement increased to 39%. Therefore, the use of PAA film and a suitable pore-widening treatment increases the light extraction efficiency of LEDs. (C) 2009 The Japan Society of Applied Physics