Study On The Material Growth Of High Luminous Efficiency GaN Based Yellow LED On Silicon Substrate

In recent years,LED has gradually replaced incandescent lamp and fluorescent lamp as the main lighting source because of its advantages in various aspects.And with the improvement of people’s living standards,the quality requirements for lighting sources are also higher and higher.And the light quality of multi-color white LED is obviously better than that of fluorescent powder white LED,which can also effectively reduce the harm of blue light.Nowadays,the wall-plug efficiency of GaN based yellow LED on silicon substrate has basically met the requirements of multi-color white LED for lighting.But compared with the blue and green LED,there is still much room for improvement,In this paper,we hope to optimize the epitaxial growth conditions of GaN based yellow LED materials to obtain more efficient yellow LED.The influences of the growth temperature of quantum barrier,the growth temperature gradient of quantum well and the concentration of Si doped in the preparation layer on the photoelectric properties of GaN based yellow LED are analyzed.The research results are as follows:1.A group of GaN based yellow LED experiments with different growth temperature of quantum barrier are designed.The effect of growth temperature of barriers on photoelectric properties of GaN-based yellow LEDs is investigated.It is found that as the barrier temperature increases,the crystal quality of multiquantum wells(MQWs)and the quality of well/barrier interface are improved,the photoelectric performance of yellow LED is greatly improved.However,the external quantum efficiency(EQE)and peak position of electroluminescence(EL)of the samples begins to decrease when raising the barrier temperature even further.One explanation may be that the higher barrier temperature reduces the nanoscale In-rich clusters in the quantum well and the well/barrier interface quality.Therefore,a suitable barrier temperature is proposed,contributing to the improvement of the luminous efficiency of the yellow LEDs.2.The effect of multi-quantum well growth temperature gradient changes on the photoelectric performance of yellow LEDs was studied,and it was found that the EQE of samples with increasing wells temperature by 2 degrees in turn is much higher than that of multi-quantum wells growing at the same temperature;The EQE decline of the samples is obvious;the samples with the wells temperature increasing by 4 degrees in turn have a slight increase in EQE at small currents,and the decrease is more obvious at high currents.Through the measurement of four samples,the results show that the change of EQE between the four samples There are some possible reasons:(1)The wavelength of light emitted by quantum well growing at the same temperature closer to the p-type layer is longer,the QCSE is larger,and the electron-hole separation is serious,which affects the EQE.when the gradient cooling growth quantum well,the electron-hole separation is more serious,EQE decline is very obvious.However,when the temperature gradient is 2℃,the wavelength of the light emitted from the multiple quantum wells is close to each other,the carrier distribution is more uniform than other samples,the wavelength and half width change less with the current,and the EQE is the highest..(2)The quantum well in near the p-layer is relatively low compared with the temperature decreasing or the same temperature,and the defect density is lower than that of the same temperature,so the EQE of the gradient heated sample increases under the small current.3.By changing the Si concentration in the preparation layer,the influence of the Si concentration change in the preparation layer on the external quantum efficiency and the forward and reverse leakage of the yellow LED device is studied.The results show that properly increasing the Si concentration in the preparation layer improves the crystal quality of the quantum well,so that the external quantum efficiency of the yellow LED is improved.The larger leakage current of the sample with less Si content is attributed to the higher defect density and poor crystal quality.