Research On High-efficiency And High-reliability AlGaInP-based LED Devices

In this thesis firstly we introduced both the light-emitting principle of the AlGaInP based Light Emitting Diode(LED)and the present situation of the mainstream technology on the market.From the industrialization,new technology and cost requirements,we need indoor displays with small spacing.Therefore,we designed a new chip with an improved brightness of the LED between traditional polarity and reverse polarity.The new chip with a small spacing is suitable for the application of high efficient combination of Current Blocking(CB)and coarsening process reliability AlGaInP LED in industry.We concentrated on the CB research and coarsening processes based on traditional positive polarity technology.The main works are as follows:In comparison with the structure of traditional polarity LED chip and current injection model of the CB current block technology,we displayed the advantages of the CB structures.According to the principles of the CB current block technology,we designed three kinds of epilayer structures with different GaP doping concentrations and different gradients.By varying the CB hole depth,the thickness of ITO,and ITO transmittance conditions,we obtained the optimal CB epitaxial structures:a surface Ohmic layer of GaP with 80 nm and a transition layer of 500 nm with a respective doping concentration of 2×1019and 7×1018 cm-3.And the favorite design is:the CB hole depth of 70 nm,the ITO evaporation temperature of 300 ?,the oxygen flow rate of 10 SCCM,and the thickness of 280 nm.Meanwhile,the CB device works very well,and the brightness improved by 17%?18%in comparison with the traditional structure.Furthermore,based on the above design of CB,we proposed the coarsening techniques to improve the external quantum efficiency of LED by reducing light reflection.Then,we optimized different technique parameters,such as ohm contact patterns,roughening solutions under different concentration ratios,coarsening depth and morphologies to improve the device performance.The final optimized parameters are as:the ohm contact with E graphic design,the C coarsening conditions fluoride(iodate three + 1 min 30 s three times),and the coarsening depth between 420?530 nm,under these conditions the brightness can improve 12.67%?15.47%.Combined with the CB process conditions,the brightness increased by 40%in comparison the traditional normal polarity one.Based on the above research work,we obtained the optimal process conditions of CB coarsening techniques,the chips with the optimized design exhibit the improved performance over the traditional positive polarity structure.The high efficiency and high reliability AlGalnP LED prepared by this process greatly improves the chip performance,meets the market demand of the existing small spacing chip and at the same time has low cost,high cost-performance ratio and obvious industrialization advantages.