High-Efficiency InGaAlP Visible Light-Emitting Diodes

Abstract
A new structure for InGaAlP light-emitting diodes (LEDs) which include a GaAlAs current-spreading layer has been designed. Remarkable improvements in external efficiency have been achieved using this structure. The photoluminescence and electroluminescence characteristics of high-Al-content InGaAlP alloys have been investigated. A GaAs substrate with an intentional surface misorientation from the nominally (100) plane towards the [011] direction was found to have a marked effect on the improvement of emission properties. The external quantum efficiency was 1.2% at 592 nm for an In0.5(Ga0.7Al0.3)0.5P active layer LED. These LEDs have been operated for more than 1500 hours at 80°C and 50 mA.