In this paper AlGaInP light emitting diodes with different types of electrodes： Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide （ITO）, but also reduces the specific contact resistances between ITO and GaP, which are 1.273× 10^-6 Ω·cm^2 and 1.743× 10^-3 Ω·cm^2 between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA.
The path of photons in the thin film （TF） light emitting diode （LED） was analyzed. The reflectivity of reflector in AlGaInP TF LED with and without the AlGaInP layer was contrasted. The absorption of the AlGaInP layer was analyzed and then the light extraction was calculated and shown in figure. The TF AlGaInP LED with 8μm and 0.6μm GaP was fabricated. At the driving current of 20 mA, the light output power of the latter is 33% higher. For the 0.6μm GaP LED, the etching of heavily doped GaP except the ohmic contact dot area is advised. The design and optimizing of current spreading between the n-type electrode and the p-type ohmic contact dot need further research.
By using the wafer bonding technique and wet etching process,a wafer bonded thin film AlGaInP LED with wet etched n-AlGaInP surfaces was fabricated.The morphology of the etched surface exhibits a pyramid-like feature.The wafer was cut into 270×270μm2 chips and then packaged into TO-18 without epoxy resin.With 20-mA current injection,the light intensity and output power of LED-Ⅰwith surface roughening respectively reach 315 mcd and 4.622 mW,which was 1.7 times higher than that of LED-Ⅱwithout surface roughening.The enhancement of output power in LED-Ⅰcan be attributed to the pyramid-like surface,which not only reduces the total internal reflection at the semiconductor-air interface but also effectively guides more photons into the escape angle for emission from the LED device.
