Fabrication Of AlGaInP Thin Film LED Chipsandstudy Of High Currentand Hightem Peraturecha Racteristics Of LEDs

Light-emitting diodes(LEDs)are devices that convert the electrical energy into light energy by radiative recombination of conduction band electrons and valence band holes in semiconductors.Compared with traditional incandescent lamps and fluorescent lamps,they have many advantages such as high efficiency,energy saving and long life.With the advancement of LED epitaxy,chip and packaging technology,the blue LED light efficiency has been rapidly improved,and it has fully met the lighting needs.Therefore,LED has changed from pursuing high light efficiency to pursuing light quality in an all-round way.The high-quality light source has the characteristics of low color temperature,high indicator,high light efficiency,safety and comfort.The use of multi-primary colors(such as:red,yellow,green,cyan,and blue)LED mixed light to prepare white light just meets the above requirements.This technical route is considered to be the ultimate solution for future semiconductor lighting.In multi-primary LED mixed lighting,red LED is an essential component.(AlxGa1-x)0.5In0.5P lattice matched to GaAs substrate is a direct bandgap material when Al composition is less than 0.53,and the band gap width is 1.9-2.3eV,which can be used to prepare red,orange and yellow spectrum Segment of light-emitting diodes.After decades of development,through the concerted efforts of epitaxial equipment,raw materials,epitaxial structure,and epitaxial process methods,the internal quantum efficiency of the red AlGaInP LED epitaxial material grown on the GaAs substrate by MOCVD method can reach more than 90%,The electro-optic conversion efficiency of the prepared power LED device exceeds 50%,which is much better than the red LED prepared by other material systems,so its industrialization degree is the highest.In addition,AlGaInP red LED can also be widely used in LED display screens,traffic lights,automotive lights,urban lighting,plant growth and other fields,with a large market capacity.In the fields of multi-primary LED mixed lighting,stage lighting and plant growth,lamps are required to emit high luminous flux,and the internal LED devices need to have good high current and high temperature operating characteristics.In view of the above,this paper has carried out research on the preparation process of high-power AlGaInP thin-film LEDs and LED high-current and high-temperature characteristics.In the preparation of AlGaInP thin-film LED chips,the research of chip preparation for N-side light emission is mainly carried out,focusing on the P/N electrode topology,the optimization of P-side ODR structure and the design of N-side electrodes;the main research on LED high-current high-temperature operating characteristics The power(EQE)DROOP,wavelength drift and other phenomena have been analyzed.In addition,the paper uses CROSSLIGHT's APSYS simulation software to conduct a preliminary simulation analysis of the internal quantum efficiency(IQE),spectrum and voltammetry(IV)characteristics of AlGaInP LED.The main research results of the paper are as follows:1.For the light shielding of the n-electrode of the AlGaInP thin-film red LED chip with N-surface light emission,the Au/Be light absorption on the ODR structure and the lateral expansion of the optimized current,this paper studies the complementary topology design with P/N electrode dislocation The new AlGaInP thin-film red LED chip based on the Ag-based p-electrode is generally set as a non-ohmic contact reflection layer in the corresponding P-side area directly under the n-electrode,that is,Ag directly contacts the SiO2 and makes the P surface non The width of the ohmic contact reflective layer is greater than the width of the n electrode,and a small hole electrode is prepared on the corresponding P surface in the middle of the n electrode strip.The study found that this improvement in chip structure design not only reduced the ineffective current injection directly under the n-electrode,but also combined with the light distribution test found that it also significantly improved the uniformity of the current lateral expansion and increased the effective light-emitting area of the chip.Performance has been greatly improved.2.This paper also studies the effect of the N-plane pad position and the number of n-electrode lines on the chip current spread.The increase of n electrode lines can improve the uniformity of current expansion.However,since the electrodes are light-absorbing,too much number will affect the light output efficiency of the chip.It is very important to optimize the number of electrodes on the LED light output surface.For a square new AIGaInP thin-film red LED with a chip area of 42 mils and 42 mils,the experimentally optimized result is that the effect of eight n-plane electrodes is better.3.In the research on the thermal characteristics of new AIGaInP thin-film red LEDs and InGaN yellow LEDs,this paper mainly focuses on the 300K-400K temperature range involved in the actual work of LED lamps.?-? temperature characteristic test found that the current transmission mechanism of InGaN yellow LED is unchanged,while AlGaInP red LED changes from diffusion-dominated at room temperature to tunnel-based.The relationship between EQE of AlGaInP red LED and InGaN yellow LED with temperature at different current densities was also studied.At low current density,EQE temperature Droop is related to SRH recombination,while at high current density,EQE temperature Droop is related to Auger recombination.Comparing the Droop temperature of the EQE of the two samples,it is found that at a low current density,the drop rate of the Droop of InGaN yellow LED EQE temperature is smaller.The reason can be attributed to the existence of V-shaped pits in the dislocation of InGaN yellow light,which can play a role in shielding the dislocation.Therefore,as the temperature increases,there are not many defects that actually participate in SRH recombination.At large current density,the reason why the AIGaInP red LED EQE temperature Droop is greater can be attributed to the faster the change of the band gap of AlGaInP with temperature,the greater the percentage change of the Auger recombination coefficient,through the theoretical formula and the peak wavelength in the experiment The relationship with temperature confirms that the AlGaInP band gap changes faster with temperature.Also studied the voltage and thermal characteristics of AlGaInP red LED and InGaN yellow LED,and found that the voltage temperature stability of InGaN yellow LED is high;In addition,this paper also studied the change of peak wavelength and half width of the two LEDs with current under 300K.4.Simulated the new AlGaInP thin-film red LED using APROSS software of CROSSLIGHT.After comparing the simulation results with the actual test,it is found that the IQE and spectrum of the simulated output match well with the actual experimental test,but the ?-? difference is large.The reason for the large deviation of ?-? characteristics may be caused by the unreasonable setting of the interface barrier of the material layer and the series resistance parameter,and the model needs to be further improved in the future.