The reasons for low output power of AlGaInP Light Emitting Diodes (LEDs) have been analysed.LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies.Two kinds of LEDs with the same active region but different window layers have been fabricated.The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency (EQE) has serious impaction on the internal quantum efficiency (IQE),because the carrier distribution will change with the body temperature increasing due to the heat inside,and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.
We propose a new method of using conductive glue to agglutinate GaAs based AlGaInP light emitting diodes (LEDs) onto silicon substrate,and the absorbing GaAs layer is subsequently removed by grinding and selective wet etching.It was found that AlGaInP-Si glue agglutinated LEDs have larger saturation current and luminous intensity than the conventional LEDs working at the same injected current.The luminous intensity of the new device is as much as 1007.4 mcd at a saturation current of 125 mA without being encapsulated,while the conventional LEDs only have 266.2 mcd at a saturation current of 105 mA.The luminescence intensity is also found to increase by about 3.2% after working at 50 mA for 768 h.This means that the new structured LEDs have good reliability performance.
