Study On The Effect Of InGaN/GaN Interface On The Performance Of Si-based GaN Yellow-green LED

Throughout the development history of semiconductor lighting technology.The low luminous efficiency of yellow and green GaN-based LED has been the major obstacle to the wide application of semiconductor lighting technology in lighting field.The widely used method to obtain the white LED for lighting is to excite the yellow phosphor powder with the blue LED.However,due to the high blue ray content,this method will lead to imbalances between color rendering index and color temperature.Moreover,it has potential risks such as "blue light hazard ".Therefore,the more balanced and healthier light source is the future development of semiconductor lighting technology.An effective method is multi-primary color(such as red,yellow,green,green,blue,etc.)synthesis of white LED technology.However,we have not yet met the requirments of this method:LEDs for each band can achieve high luminous efficiency.At present,neither the InGaN material system nor the AIGaInP material system can achieve higher luminous efficiency in the yellow-green band,which is also the difficulty of multi-primary color synthesis of white LED technology.In this paper,based on the great breakthrough on the previous research,we studied the influence on the interface quality of InGaN/GaN preparation layer and quantum wells as well as the photoelectric performance of long-wavelength LED,in order to improve the luminous efficiency of long wavelength LED.The following research results have been achieved:1.By introducing different time of H2 into the growth process of GaN barrier in preparation layer,the effects of H2 on the preparation layer's interface quality,quantum wells' crystal quality and photoelectric performance of yellow-green LED were studied.It is found that the incorporation of Indium in the quantum wells can be improved by introducing longer H2 treatment time during the GaN barrier growth process of the preparation layer,and the interface quality was improved.Moreover,it can improve the crystal quality of the side-wall quantum wells,effectively inhibit the leakage of electrons to p-GaN,thus improve EQE.At 35 A cm-2 current density,the external quantum efficiency(EQE)of sample with H2 treatment time of 20 s and sample with H2 treatment time of 60 s were 22.78%and 24.52%,respectively.2.By optimizing the growth conditions of GaN barrier in the InGaN/GaN superlattices(SLs)preparation layer,we obtained high quality preparation layer,so as to improved the crystal quality of quantum well and obtained high luminous efficiency of yellow and green GaN-based LED.According to the experimental results,when the two-step varied-barrier-growth temperature method is used to grow GaN barriers in SLs,the interface between InGaN layers and GaN layers became more abrupt,and the indium distribution in the quantum wells became more uniform.In consequence,the forward voltage was reduced,the external quantum efficiency(EQE)was improved.By decreasing the growth rate of the high temperature barriers,the indium uniformity became even better,forward voltage was reduced again and EQE was further improved.At 35 A cm-2 current density,the EQE of sample which were grown by the traditional method is 24.14%,the EQE of sample which were grown by the two-step varied-barrier-growth temperature method is 27.24%,the EQE of sample which growth rate of high temperature GaN barrier were reduced is 28.4%,respectively.3.The effects of different thickness of n-AlGaN inserted after the preparation layer on the epitaxial thin films properties and photoelectric properties of yellow and green GaN-based LED were studied.It is found that the increase of n-AlGaN thickness can improve the interface quality of quantum wells and barriers.According to the previous simulation results,the insertion of n-AlGaN can make the carriers distribution in quantum wells more uniform,increase the hole concentration,thus improve the EQE at low current density.Meanwhile,the increase of n-AlGaN thickness will also increase the size and density of V-pits in samples.Because the thickness of n-AlGaN at the side wall of the V-pits is thinner,the energy potential barrier is lower than platform,which will lead to an increasing ratio of electrons injected from the side wall,result in electron leakage,thus adversely affect the EQE at high current density.Although the EQE of long-wavelength LEDs has made great progress,the EQE of long-wavelength LEDs is still lower than that of blue light LEDs.By optimizing the growth conditions of InGaN/GaN preparation layer,the interface quality and crystal quality can be effectively improved,and the luminous performance of LED can be improved.In the subsequent research,it is necessary to further improve the EQE of long-wavelength GaN-based LED by means of interface regulation with the purpose of improve the interface and crystal quality and regulate the injection of carriers...