Emission Spectrum Regulation Of Yellow-green Dual Wavelength LED

In recent years,LED devices are widely used in backlight lighting,display,array projection and road lighting due to their small size,high efficiency,energy saving and long service life.However,after years of research and development,the market demands for lighting have gradually shifted from high brightness and high light efficiency to a more energy saving,healthy and intelligent human factor lighting mode.Because of its unique potential,multi-color led hybrid white lighting mode based on all semiconductor electroluminescence has been widely pursued by researchers.However,there are some problems such as uneven mixing light,high production cost and complex driving circuit.In order to solve the above problems,a feasible solution is to use a single chip dual wavelength or multi wavelength LED chip.Based on the self-developed high light efficiency yellow LED,a single chip yellow-green dual wavelength LED is developed in this paper.Through the change of p-GaN spacer layer,the penultimate barrier component and the structure change of yellow and green quantum wells,the regulation method of single chip yellow-green dual wavelength LED spectral characteristics is studied,and the research results are as follows:1.By inserting p-GaN layers of different thickness between Electronic barrier layer(EBL)and Multiple quantum wells(MQW),the effect of p-GaN insertion layer on the emission spectrum of single chip yellow-green dual wavelength LED was studied.The results show that although the p-GaN spacer layer does not significantly affect the thickness and crystal quality of MQW,it can play a buffer role,reduce the stress of EBL on the green light well,affect the distribution of carriers in the active region and reduce the blue shift of the green light peak in the device's Electroluminescence(EL)spectrum.However,in the case of high current,the existence of p-GaN spacer layer weakens the electron limiting ability of EBL and leads to electron leakage.In addition,the existence of p-GaN spacer layer results in the position of p-type layer far away from the active region,and the depth of hole injection becomes shallow,which leads to the decrease of external quantum efficiency.2.By introducing AlGaN insertion layer into the penultimate quantum barrier,the influence of AlGaN insertion layer on the photoelectric performance of single chip yellow-green dual wavelength LED is studied.The results show that the AlGaN insertion layer has no obvious effect on the thickness and crystal quality of MQW,but it results in the increase of lattice mismatch,which intensifies the piezoelectric polarization,and leads to the longer light-emitting wavelength at low current at room temperature.In addition,the AlGaN insertion layer has formed a higher barrier,which can restrict the carriers.Part of the carriers are better confined to the end well for radiation recombination.Under the condition of high current at room temperature,the existence of green light peak can be observed in the El spectrum,which indicates that the AlGaN insertion layer can play a certain role in regulating the carriers.However,the AlGaN insertion layer will also cause the light intensity of the device to decrease slightly,increase the additional barrier,and lead to the rise of the forward working voltage.3.By changing the number and types of the composite quantum wells in the active region,the influence of the well structure change on the photoelectric performance of the single chip yellow-green dual wavelength LED is studied.The results show that adding a yellow light quantum well in the active region will increase the yellow light quantum well participating in the radiation recombination and improve the external quantum efficiency,but it will increase the series resistance of the LED devices,and the positive working voltage will rise with it,but it has little effect on the El spectrum.A green light quantum well is added to the active region,and the quantum efficiency is slightly reduced outside the high current density,which will also increase the working voltage and intensify the polarization effect.However,the existence of green peak can be observed under the high current density at room temperature,which indicates that in addition to the radiation compound luminescence of the carrier in the yellow light quantum well,the green light quantum well also participates in the luminescence.It can be seen that the green light quantum well also participates in the luminescence The change of structure can play a role in the regulation of carriers.Although the research of single chip dual wavelength LED has made some progress at present,there is still a big gap in the flexible adjustment of spectrum configuration.It is still necessary to carry out in-depth research on growth methods and epitaxial structures around how to better control the injection,distribution and radiation recombination behavior of carriers.